Flopping Trips / Set
If you flop trips with two same-suit cards on the board, you should be slightly over-betting the pot to put off those players on a flush draw. Its better to win the pot here than find yourself chip-committed against a flush on a more expensive turn or river.
Again, if you flop trips but with a straight draw on the board, you should bet / raise for the same reason.
Some people choose to slow play their trips. This is not a good idea. Check-calling will not make you as much money as if you bet it out. Players with TPTK are likely to pay you off. Trips are dangerous because although they are likely to be the best hand on the flop, they might not be by the river. Bet them hard and aggressive but be prepared to lay them down if the board makes four-to-a-flush.
Flopping a Straight
Don’t make it cheap for the flush drawers out there to see the next card. If you flop a straight but there is danger of being beaten by a flush, raise it up and play it aggressively while you have the best hand.
If you flop the low end of the straight, raise up the pot to try and protect against people drawing to the higher end of the straight.
Examine the flop carefully. If it comes down non-connected and rainbow you can afford to play it a little slower. If it comes down same-suit and/or connected then play it hard to push out those drawing to a better hand.
Flopping a Flush
Bear in mind that it takes 5 cards to make a flush, there are only 8 cards left of that suit in the deck. It is possible but unlikely that another opponent also has a flush. Play low card flushes with caution and get your money in the pot while you still have the best hand.
If the flop makes three to a flush you should bet / raise to gain information and to win the pot early on.
If your flush is low (7 or lower) then be prepared to lay it down should the board make four-to-a-flush and someone is betting it hard. You are most likely up against a better flush.