The decision whether to raise, call, go all-in, or limp pre-flop depends on many different things. Some responses here say you should fold weak hands, which I think is a wrong advice cause then you would have to define a range of "weak hands". The problem a chart of "weak hands" without context is useless cause a profitable opening range differs *a lot* depending on certain factors. A few most important ones are:
* your position
* your stack and stacks of your opponents
* the type of the game (online/live cash game, tournament etc)
* population/table tendencies
Typically, you want to raise to either see the flop or get the blinds if everyone else folds. The earlier the position, the bigger the chance that someone else calls or 3-bets, thus your range has to be fairly small. When you are on UTG in a 9-max game there are 8 people that can potentially call or raise you. If you are on the button, there are only two. The next thing to take into account is your stack and stacks of your opponents. If you have 100BB or more you can probably open a bit wider than when you are at 40BB. At 20BB and less, there are certain hands that you might want to get all-in. The next thing is the type of game. For example ranges will differ between a cash game and a tournament, mainly because of antes, but might also depend on the structure. In a fast tournament when the blinds increase every few minutes, you might want to play more aggressively - if you are too tight you might not lose much, but your stack will quickly shrink to 10-20BB if you don't win anything. The next thing is what's a tendency of players you play with - either the table or the population. Opening ranges will differ drastically depending on stakes. For example, on higher stakes people tend to open closer to standard ranges. On very low stakes there is more polarization: more people that play extremely tight (like VPIP < 15%) or extremely loose (like 40-50% or higher). If you play on a very tight table, it might be profitable to raise weaker hands as a
bluff. Especially on late positions. If SB and BB are playing very tight, you might collect the blinds quite often. Also, from what I experienced on lower stakes people will typically 3-bet less often.
These are the most important reasons that you can base your opens on, but it also does not tell you that much if you're not experienced. Yeah, I just told you that you have to play tighter on UTG than on the button, but what does it really mean? Do you only raise a few top hands on UTG? Do you raise with anything on the button? Because it's not easy to answer these questions just by playing poker, I *strongly* recommend finding a set of pre-flop charts online, and studying them once in a while. You don't have to remember every single hand on every single position, but even roughly knowing the types of hands you should open with will make it easier to figure out what to do.
One interesting example is JT. There is a
thread here asking whether to raise JT or not. There are a few answers saying it's a weak hand that you should fold. But when you look at most pre-flop ranges, when you're playing deepstacked, you should raise JTs from pretty much any position and you should raise JTo should raise from late positions. If you follow the advice from those tighter players you would be probably loosing value by just folding JT, especially the suited version.