Combat as an enemy foot soldier
Unless given specific instructions, the grounds of playing a basic enemy unit should always include a little resistance, only momentarily demonstrating being a capable soldier. From there, ramp down slowly until you are defeated. You can make the motions of applying a few "jabs" in the events of combat, and show a few successful parries. The ultimate goal is to remember that the players are typically above the skills of basic units.
Combat of more difficult enemies
In some cases, GMs may give specific instructions to vary the difficulty you can show as an enemy unit. In these cases, you should adapt as instructed. Unless given the strict GM command to win, you should still always play to lose, simply ramping your received damages and given hits at a much slower rate. In many cases, a GM may give you direct instructions if you are playing either a mini, or big bad boss. Sometimes you might have to choreograph events ahead of time as well, giving a rigid path to follow so the GM can concentrate on fewer major adjustments rather than meticulous events.
Melee:
Blades
Spears
Maces
Axes
Short Medium Range:
Crossbows/Bolts
Flintlocks
Long Range:
Bow/Arrow
Which each weapon range category can be broken down into more in depth divisions, such as a spear vs a dagger, for roleplay purposes, the play to lose/win or GM override effect guides the more specific differences.
Short Range
Some magic can be casted at a short distance, such as throw of flames or dispersal of energy.
Long Range
Things like Firebolts can be used to send a small concentration of fire which contains itself until it makes contact, rapidly expanding into a larger coverage of area from the contact point.
Area of Effect
Surrounding the caster or origin point, some magic affects the area from which it was case or set off from. Magic that creates a field, or perhaps the result of a Firebolt from its impact are to be considered in these moments.
Receive your strikes:
When you receive hits or strikes, you must lift your sword as if blocking, or receive the hit. No matter what weapon types or boosts you might have, standing stone fashioned is definitely of poor form. Even if you think a strike might not have landed, giving a flinch at least can help communicate with your fellow combatant that something is happening.
"From behind":
Always make someone aware a moment ahead of time if you do something from behind. Avoid doing anything from behind if possible if you are not a specialized NPC.