The first thing you should do on your turn is to look at the chop cards of everyone on the team.
Are there any cards on chop that need to be saved (or played)? If so, do you have to do it, or can someone else do it?
If no-one else can do it, then you need to give the Save Clue (or Play Clue), even if you have a card to play.
If someone else can do it, would it be better for you to save the card, or for them? If they have a card to play and you do not have a card to play, then it is better teamwork for you to save the card.
In general, if you have a choice, color clues should be given over number clues. This is because color clues are usually more specific, telling the player the exact identity of the card.
Of course, don't be afraid to disregard this advice and use number clues if it "gets" additional cards or it helps to "fill in" other cards in the hand.
Don't be afraid of discarding. If you discard something important, it won't be your fault - it is your teammates' responsibility to save any important cards.