Goals vs. Win Conditions
Most RPGs have a goal in play, but not a win condition (a few do, though). Consider the difference between a game about Greek warriors and making a story about their struggles vs. a game about Greek warriors played for tactical success. Figuring out what the Goal of the game is, tells you what good play for the game will be like.
The biggest hurdle, not just for wargamers, but everyone, is that many of the game rules are designed (...or, in some cases...un-designed) to potentially fulfill different roles in this way, so you may need some discussion up front to be clear on exactly what good play looks like for this particular game group.
Clarity on Game State
One of my friends who is a big wargamer pointed out that key point of play in that hobby is clarity on "the game state" - where every character stands, what the conditions are, etc. Clarity is necessary to make better decisions.
RPGs on the other hand... are often more fluid. The reality is that much of what happens in an RPG is because the group consents to that being true. This makes it more tricky to handle - a good game has a clear focus on goals so everyone knows what parts demand clarity vs. what parts are not that important. If you're playing a game about soap opera style drama, the important things are what everyone's relationships are to each other, and who's lying to whom, etc. but not what they're carrying or how strong they are. Spending too much time focusing on things that aren't relevant to the game disrupts play.
Genre Expectations Matter
RPGs often give you the option to do many things, but good play is often bounded by expectations within a given genre. For example, if you're playing a game about Golden Age Superheroes and you start destroying buildings full of innocent people just to kill the bad guy - that's bad play.
It's worth noting that some expectations are supposed to never be violated, and some are to be stepped over, but only as a Big Deal (TM) - and some are not even in play at all. Again, a good understanding of what the game text advises and a discussion among the group helps a lot.
Optimize/no don't optimize
Many RPGs suffer from a problem of having strong optimization rules built in, but then the advice around the game is to not use it. This is generally a bad game design set up, but it does make up a lot of games trying to cater to two different crowds. Talking to your group and the GM to figure out what they're looking for is key, but it's also worth noting that several games with this problem also punish poor choices severely - a character that's too far below the expected curve will die quickly, or be a 3rd rate character the whole campaign - as you are often locked into particular builds early on.
I don't really have a simple answer to that, as it's both common and endemic to many designs and often groups are terrible at really getting into how far the expectation is to go one way or another with it.