Welcome to the DoDs side!!! The game is a bit more fast pace compared to INS. The maps are laid out about the same way but DoDs is a bit more bottle necking with the flow of people.
A good gun to start off with to get use to the recoil would be any SMG. If you have that Unreal Tournament twitch style game play try the rifle/sniper rifle. The sniper rifle is most of the time one shot one kill as long as you don't hit a limb... The German k98k is the same but with out a scope (one shot one kill) but is slow reload of the next round just like both sniper rifles. The American rifle on the hand takes about 2 shots to kill someone (80 damage if hit in the chest) but it is semi auto so you can keep firing away.
Well that is just my starting guide to get you started with. Enjoy the game, familiarize your self with the maps, and last HAVE FUN!!!