Betting and Raising.  Raising or betting can be done for four reasons:  1)  You are on a draw to the nut-flush and want to build the pot up;  2)  To buy a free card on the turn;  3)  You have flopped top pair with your flush draw;  4  You think a bet can win you the pot.

When you are on a draw to the nut-flush,  consider a bet to build the pot up. This is a good move in a particularly passive game where you will get many callers. Admittedly,  being a tight player I find this can be tough to do at times, but by betting when you know you will get many callers,  you get more bang for your buck.  For instance,  suppose you hold AQ of spades,  and the flop comes 9-7-4 with two spades.  You are in late position in a $2/$4 game with $1/$2 blinds and six players have seen the flop,  meaning there is $12 in the pot. (We’ll assume this is a home game that is not raked;  of course if the game were raked there would be slightly less than this in the pot,  but your strategy would be the same.) Your instinct may be to check,  because you do not have your flush yet.  But if you believe the other players will all call,  bet.  If you check and there is no action,  the pot stays at $12.  However,  in a loose-passive game,  if you bet and get several callers,  you increase your pot odds.  The odds you will make the hand by the river are about 1.6-to-1.  A bet right now into the pot gives you pot odds of 6-to-1;  these will only increase as you get callers.

A bet or raise can also be used as a semi-bluff,  and buy you a free card on the turn when the betting limits increase.  For instance,  in the above situation,  if you were in late position with your four-flush,  a bet might not only get several callers but get you a free card on the turn,  especially if you showed aggression before the flop by raising  (which you should do with AQ).

If you flop top pair with a flush draw,  you’ve flopped a very powerful hand.  Some prefer to slow-play this in hopes of winning a large pot.  Gambling is justifiable, and you can do this in very tight games,  but most of the time simply bet or raise if you flop top pair.  You will usually get several callers wanting to see the turn, and if you win the pot right there,  there’s nothing wrong with that.

Finally,  if you think you can win the pot with a bet or raise,  go ahead and take a chance.  While most games at the low limits are loose,  you do run into tighter games from time to time.  The best time for this play is when you are last to act and are not up against sophisticated players who may check-raise you.

Calling and Folding.  Most of the time,  you will be calling with your four-flush on the flop and turn.  When action begins to get heavy,  situations come up where you need to consider laying down your hand unless it is to the nut or second-nut flush  (ace or king-high),  because depending on what the board is showing, you may be up against a bigger hand or better draw.  These are rare situations, but they do come up.

One scenario is when there are three suited cards on the board,  and you hold a small card  (nine or smaller)  to the flush and have no chance at a straight flush or full house.  For instance,  let's say you are the big blind,  holding 84 offsuit. The flop comes 7-Q-K,  all diamonds,  and you have the four of diamonds.  The little blind checks,  as do you,  and the player to your left bets.  Three others call, and it's back to you.  It may be tempting to call,  but if you get another diamond with four other players in the pot there is a good chance that your flush will not be good.  Save yourself the money.

When you have two suited cards in the pocket,  the smaller they are the more often you may fold.  Typically this will occur when you have limped in with small, suited connectors and the board has paired.  For instance,  you could have 56 suited from late position,  and the flop comes J-J-9 with two of your suit.  If it is just one bet go ahead and call,  especially if the pot is large,  but if it is two bets or more get out of the way,  as you could be up against trips.

If you do not make your flush on the turn,  it is worth one more bet to see the river most of the time,  but again you must be alert for clues that your hand may be second-best if you make it.  Again,  the biggest clue is heavy action on a paired board.  Obviously,  if you are looking at trips on the board,  you will typically be folding if there is a bet because there is an excellent chance you are beat.

River Play.  Your course of action is usually fairly obvious on the river.  If you hit your flush,  you raise and bet;  if you do not,  you fold.  However,  there are some exceptions.

One is,  again,  when the board has trips showing.  Here you have to be very careful,  and you want to play passively,  especially if the field is large,  checking and calling for a bet,  and folding if there is heavy action.  You can bet if it is checked to you and you are last to act,  and believe your flush is good,  though.

Another situation in which you can call rather than raise is when you feel you have a good read on a player and believe he has a boat.  Obviously,  the board will have to have a pair showing in order for a player to have filled up,  but there is nothing wrong with calling as opposed to raising on the river when you feel you have a read on a player.  (Most of the time,  though,  with a big flush you will be raising and then calling if re-raised,  rather than just calling.)

Finally,  you can fold your flush if there are four cards of your flush on the board, your flush is weak,  and it looks like your flush will not be good.  The biggest indicator of this is heavy action.  For instance,  you hold 75 suited;  you limped from the button,  and made it to the river because play was passive.  Now,  one player bets and another raises and four cards of your suit are showing.  It is tough to make the laydown, but heavy action means another player surely has a flush larger than yours.  (Always call for one bet,  though,  as losing one more bet is not a big deal,  but losing an entire pot is a colossal mistake.)

Are you beat?  Finally,  you need to be aware of what the board is showing at all times,  and how likely it is you may be beat even if you make your hand.  When the board pairs and there is heavy action,  you have to consider laying down your hand based on the knowledge of your opponents,  how they acted in previous betting rounds,  and how big your flush draw is.  You will not fold for one bet if the board is paired and you are on a big flush draw,  but if action gets very heavy on the flop or turn,  there is nothing wrong with a laydown.  There is no point in drawing to the second-best hand.