Tactics depend on which game mode, your skill, your reaction time, set up etc. but generally I would say play how you want to play. Hanging back and being cautious is useful and a good way to play when you are new to a game, especially when your opponents aren't new. As a general rule though I would say running around you will come across more players and so get more kills though you will also most probably die more. Hanging back will remove some of the risks so you wont die as much but then you will get less kills too.
Personally I tend to stick to TDM or domination. TDM I generally run away from my team and try to be on the otherside of the map to them. It is a high risk high reward tactic but the most fun way to play it IMO. Domination is a bit of the same but I am happy to sacrifice my k/d if it means getting an objective. Once you have an objective though it is all about holding it so then you can be more defensive.
