Always go for a custom torso. The limbs can be basic CCBS/Inika build, but the torso must be custom. There are some exceptions, though, like if I’m trying to replicate a specific build (for example, a Mata Build Toa)
Placeholder masks. I never paint pieces unless I absolutely have to, so if I’m making a Toa of Plasma with a Kualsi and the Kualsi doesn’t come in orange or white… give it a mask that does.
Use what you have. If you’re making a character who’s supposed to be orange and tan, don’t give him technic-heavy limbs full of parts that come in neither orange nor tan.
Use red axles when they’re hidden, or when the character is red. Use black axles if they are visible from the front/sides. (ideally this would apply to blue, but the black pin/axle adaptor is so stupidly rare…)
Use 01-07 style Sockets if at all possible. If you must use 08 sockets or CCBS sockets, make sure they match (I.e don’t use an 08 socet for one hand and a CCBS socket for the other hand)
Function follows Form. I don’t want a moc that looks good on a shelf but will fall apart if you try to pose it, or just can’t pose. I actually play with my mocs and pose them, maybe recreate story scenes.
silver is to be avoided unless the character has silver as part of their color scheme or it’s a weapon. In other words, silver armor is fine for a Toa of Iron, but don’t slap silver armor on a Toa of Earth due to a lack of parts
Ekorak must die first in any Mafia game.
If you’re gonna go asymmetrical, go full ham. Only have one orange foot and one white foot? That’s fine, so long as the legs and shoulder pads and arms are mismatched too.
If a design uses a rare and useful moccing piece, at least think if there’s any other option before you use it.
This is the most important rule of all: Tahu MUST be green.
Don’t purposefully damage pieces, but if a piece is already tarnished, try to use it somewhere
Anything built must have a decent level of sturdiness and poseability (wait, poseability isn’t a word!?).
When making a bonkle, try to make it canon-compliant. If it doesn’t fit into G1 canon, throw it into the HF universe
When making a vehicle, make sure it can accommodate at least 2 people. I dunno, it just makes me sad whenever there’s just one driver who’s got nobody else to talk to.
Those are just my personal guidelines. If you want to hot-glue metru canister bobs to your moc, I won’t try to stop ya.