Sample Build for Mekton Zeta:

1: Set Concept: This will set the tone for the whole design, and you can check goals along the way to make sure you're not missing anything.  Concept can be as broad as "A fast mecha with plenty of power" or a full write-up with bullet-point design goals.

For this design, I'll make a light combat mecha called the YF-38A Fox.  It can transform into a fighter jet for fast deployment and carries a rapid-fire gun pod/rifle (based on the GAU-12 Equalizer 25mm gun pod), a heat knife, an internal missile bay in each leg carrying two missiles (AMRAAMs) and a missile bay in each arm also carrying two missiles (Sidewinders).  The design is composed to be analogous to modern technology, so no alterations from the basic Mekton rules will be needed.

2: Construct a Frame:

2A: Choose a body form: Since the Fox has a humanoid mode, we choose "humanoid" as its default build form.  This means that it has two arms, two legs, a torso and a head.  To accomodate its transformation into a fighter, we buy two wings and a tail (the tail represents the entire tail assembly).

2B: Buy servos: "Servos" in Mekton-speak are the body sections of a mecha.  Since we're building a small, lightweight mecha, we choose Lightweight servos all around.

Servos
Servo
 Class
 Cost
 Space
 Kills
 Melee+
Torso
 Lightweight
 4 cp
 4
 4
 n/a
Head
 Lightweight
 2 cp
 2
 2
 n/a
Right Arm
 Lightweight
 3 cp
 3
 3
 +0
Left Arm
 Lightweight
 3 cp
 3
 3
 +0
Right Leg
 Lightweight
 3 cp
 3
 3
 +0
Left Leg
 Lightweight
 3 cp
 3
 3
 +0
Right Wing
 Lightweight
 2 cp
 2
 2
 n/a
Left wing
 Lightweight
 2 cp
 2
 2
 n/a
Tail
 Lightweight
 2 cp
 2
 2
 n/a

Now you may have noticed something peculiar: When dealing with structural components, 1 cp = 1 space = 1 kill.  This is not always so, but it's a good rule of thumb to keep in mind.  In all cases, weight in tons = kills divided by 2, so here, we have (4+2+3+3+3+3+2+2+2)/2 = 12 tons for basic structure.

2C: Buy wheels and treads: Because this mecha is not intended to use wheeled transportation as its primary movement in any mode, we don't have to buy wheels.

2D: Buy armor: A fighter typically has light armor or no armor at all.  The Fox carries Lightweight armor - just enough to protect it from light gunfire for a short period of time.  If a Fox pilot wants to survive on the battlefield, he's going to have to carry his wits sharply about him, and evade enemy fire.

Servo
 Armor Class Stopping Power
 Damage Coefficient
 Cost
Torso
 Lightweight
 2
 1
 2
Head
 Lightweight
 2
 1
 2
Right Arm
 Lightweight
 2
 1
 2
Left Arm
 Lightweight
 2
 1
 2
Right Leg
 Lightweight
 2
 1
 2
Left Leg
 Lightweight
 2
 1
 2
Right Wing
 Lightweight
 2
 1
 2
Left Wing
 Lightweight
 2 1
 2
Tail
 Lightweight 2
 1
 2

Unlike structure and virtually every other system in the game, armor neither provides nor uses spaces - it is simply there, part of the design.  The armor's weight equals (2*9/2) = 9 tons.  The total frame weight of the mecha is (12 + 0 + 9) = 21 tons.  The total frame cost of the mecha is (24 + 0 + 18) = 42 Construction Points.  The mecha itself has a total of 24 spaces available for equipment, one of which (which I'll get to in a minute) is pre-committed.

The "Damage Coefficient" column represents how much damage a piece of armor must take in a single hit before its stopping power degrades by 1 Kill.  There are five types: Ablative, Standard, Alpha, Beta and Gamma.  For Standard, Alpha, Beta and Gamma armor, each hit degrades one point of stopping power, regardless of how much damage is stopped or how much damage penetrates to the servo underneath.  Ablative armor loses one point of SP for every point of damage it absorbs.

The one pre-committed space in a mecha's design is the cockpit.  Unless you're designing a mecha with Internal Automation (a multiplier system, see below), every mecha MUST have a cockpit, which as we all know from watching anime is just large enough for one person (usually the hero) to sit in while holding a second person (usually his girlfriend) on his lap.

3: Choose Your Weapons:

3A: Build Weapons.  Go to town.

3B: Do they fit?  Probably not.  Spend some extra CP for Space Efficiency, trim down the cost of your weapon, or some other method of getting it to fit (such as making it handheld).

Hands: Hands in Mekton Z are purchased as melee weapons:
Damage: 1K
Kills: 1
Accuracy: 0
Modifiers:
Quick: x2.0
Handy: x1.5
CP/Spaces: 1.5
Space Efficiency: -0.5 spaces
Cost: 1.75
Spaces: 1
Location: Arms.  Duh.

You can also create a Handy melee weapon without the Quick modifier to build a hardpoint.  It's a bit of a kludge, but it works.

Feet do not have to be purchased - they're assumed to come with the legs.

Main Gun: GAU-12/E 25mm gun pod This is a modified variant of the gun pod carried by the AV-8B Harrier II+ jet attack aircraft.  Its rate of fire is represented by a burst value.  Now, because the milieu of this mecha is a quasi-modern setting, "burst value" is somewhat of an abstraction.  This gun will have only six "bursts" available to it, representing 30 seconds worth of ammo.

Damage: 1K (firing a 25mm shell)
Kills: 1
Accuracy: 0
Range: 6/36 (0.3km primary range, 1.8km effective range) (x1.5 cost)
Burst Value: 3 (an extreme abstraction, obviously) (x2.0 cost)
Ammunition: 6 bursts
Hypervelocity (x1.5 cost)
Cost/Spaces: 6
Location: 2-handed (battloid mode), underfuselage mount (fighter mode).*
*: Like on a VF-1 Veritech in Robotech

AIM-120 AMRAAM missiles: This is the point where things get kind of hairy, and we're going to have to use a lot of space efficiency to accurately simulate the AMRAAM, which has a maximum engagement range of 32 kilometers (1600 hexes!).  Fortunately, if you've been paying attention, the extended range of most Mekton weapons is equal to the primary range squared, so we only need to buy primary range up to 40 hexes (2 km).  So we start with a 5 Kill missile (0.5 cp, range 8) and buy a 500% range increase (cost x3.0).  That raises the cost of the missiles to 1.5 cp per missile, or 3 cp for both.  Unfortunately, we can't PUT 3 spaces worth of missiles in the legs, because we're going to need two spaces for the engines later on.  So, we spend 1 cp to Efficiently remove two spaces, from the missile mount, fitting a pair of fairly deadly missiles in one space.  Repeat for the left leg.

Damage: 5K
Kills: (5*2/15) = 0.75 kills, round to 1 per launcher.
Accuracy: 0
Range: 40/1600 (2km primary range, 32km engagement range)
Ammunition: 2 missiles per leg, 4 total.
Location: Right leg, Left leg
CP/Spaces: 3
Space Efficiency: -2 spaces
Cost: 4 cp each
Spaces: 1 each

AIM-9 Sidewinder missiles: The AIM-9 is a much shorter-ranged missile; extended engagement range of 18 kilometers (360 hexes), requiring a base range of 18 hexes.  Because Mekton Z doesn't have a cost modifier for a range increment of 300%, I'm going to fudge it and say that 300% range is x2.0 cost; so the four 3-kill arm-mounted Sidewinders cost 0.6 construction points apiece.

Damage: 3K
Kills: (3*2/15) = 0.4 each
Accuracy: 0
Range: 18/360 (0.9km primary range, 18km engagement range)
Ammunition: 2 missiles per arm, 4 total
CP/Spaces: 1.2 per arm (round to 1 space per arm)
Cost: 1.2 cp each
Spaces: 1 each

Heat Knife: A basic light melee weapon for fighting other mecha.  The heat knife is battery heated.

Damage: 2K
Kills: 2
Accuracy: 0
Range: Melee
Ammunition: N/A
CP/Spaces: 1

At this point we have all our weapons, so we can total up cost and weight:

Cost: 1+2.4+8+6+4 = 21.4
Weight: (2+1+2+1+1+1)/2 = 4

At the end of step 3, we have a mecha that costs 63.4 cp and weighs 25 tons.

Step 4: Consider shields

Since this mecha is being designed at a modern level of technology, reactive shields aren't appropriate, and because the design is intended as an air to air dogfighter, neither active nor standard shields are appropriate either.  We will therefore not equip the YF-38A with shields.

Step 5: Buy Crew and Sensors:

The YF-38A is intended to represent a single-seat fighter; so we will reserve one space in the torso for the pilot and designate the cockpit to be a "canopy" type; meaning that the pilot is protected only by bullet-proof lexan instead of the fighter's armor.

Because the longest-range weapon of the YF-38 has a maximum range of 32 kilometers, its sensors have to have a longer combat range than the weapons - going down the chart, we see that Superheavy sensors are the first sensor system whose range exceeds the AMRAAM's.  We install Superheavy sensors; which cost 27 CP, have 3 kills and take up 1 space; into the head.

At the end of Step 5, you have the following spaces left:

Head: 1
Torso: 3
Right Arm: 1
Left Arm: 1
Right Leg: 2
Left Leg: 2
Right Wing: 2
Left Wing: 2
Tail: 2

Looks simple, so far?  Just wait, there's more to come in part 2...