A few things.
North runs with one hand on the weapon, South runs with two, this is not reflected in the first person view for some reason.
Keep an eye out for sillouttes, they do have some key differences.
Some things to look for:
- PAVN uses tan and dot camo for now, they did have a jungle green, but it's not included for "Balance reasons".
- NLF uses black/blue civ clothing, will always wear a neckerchief and tend to have fabric cover helmets or soft caps.
- PAVN tends to have flared helmets, or soft tops.
- Northern Rucksacks are lower and have a more slouched look, while Southern ones are squared and just about shoulder height.
- US army used OD, while Marines used Woodland. Always have camo hats, hard or soft.
- Aussies almost entirely use boonies, which makes them harder to stand out from their enemies.
- Only Southern forces have darker colored skinned individuals.
Now there are a few items which can help you look like an enemy, which can help with sneaking/flanking but will make you much more susceptible to team kills.
PAVN - Cap, SSh-39, tiger striped hat.
South - Tiger striped cap, bandanas.
- Going shirtless on either side, unless you picked the darker skinned characters.