As a relatively inexperienced player myself, and with the influx of new people into the forum, it seems to me that it would be a good time to start a thread with some tips for newer players. Not so much very basic strategy, but rather things and tricks that may not be obvious to someone first playing the game / learning the rules.
(Sorry if there's already been a thread like this, but I didn't see one in my first look through this forum.)
Are there unit types or skills that are more useful than they seem? Traps or point sinks people are likely to fall into? I think those sort of tips would be very useful for newer (and maybe even intermediate) players.
I'll offer one example from personal experience: I know I totally overlooked the strategic possibilities of minelayers. Thinking back now, there's a number of games where I would have had a lot more success having deployed some mines in or around my deployment area - it would have thwarted a number of rambo runs by opponents.