This is exactly what I've been finding out. After playing so many games, things just seem to come more naturally. I tend to adjust to whatever everyone else is doing. If I spawn after a rush has already left, I'll stay back and defend the base.One thing I've started doing.. always use your timed C4.. somewhere.. anywhere. You'd be surprised at how many kills and how much damaged I've caused because of that. I'll drop one in the middle of no where since a sniper is obviously targetting me (survived the first shot). Then a little bit later I get a boink. I love to have tanks run me over, but I usually always leave a little present stuck to their front end. yeah.. I'm that suicidal soldier you see running at the tanks and jumping just before they hit me.
Unfortunately some people haven't played long enough. Techs, for instance, should be protected by their infantry escorts.. not ignored. I was a tech in a C4 rush and when we encountered an enemy infantry unit (basic gun), I backed around a corner only to have the enemy follow me and kill me. My teammates just kept on running and completely ignored the enemy that was attacking me.