So, here's just a few tips when it comes down to starting a team.
Communication - This is vital for a team. Everyone needs to have situational awareness and constantly talk to each other. If one person is out of it, everything falls apart.
Uniforms - All team needs a set standard of camouflage. Multicam, ACU, M81 Woodland, FG ATACS, black, white, pink. Whatever it may be.
Gear - Matching gear isn't always going to work out due to everyone's preference. Try to maintain the same gear color (CB, FG, TAN, KHAKI) and gear style. You don't want people going around in black FLC with a tan base ball cap and white boots.
Leadership - You have to designate team leaders and subordinates. Don't be afraid to have leaders and people under them. It's perfectly fine to have everyone put in their opinons but if people start questioning each other in the heat of battle, it can go wrong fast. It makes for a more organized team.
Weapons - This may be a bit harder since everyone has a weapon of choice. Try to allow it so everyone uses the same magazine type. My team and I all use M4/M16 magazine compatible weapons as well as sidearms. This helps with sharing magazines throughout the game, especially Milsim.
Fireteam Roles - Again, this is up to you guys. You can designate shooters as SAW gunner, marksman, rifleman, etc.
It's all about looking good and having constant communication. If either of those go wrong, you lose the advantage of fear.