It’s often a good idea to make an overcall at the one level. It usually helps partner get off to a good lead if you end up on defense. You may even find a safe partial contract, game, or sacrifice in a competitive auction. Overcalls interfere with opponents’ communication, particularly if the overcall is one spade. Overcalls don’t necessarily promise an opening hand. They are in the range of a good eight to seventeen points with most of the strength in the overcalled suit.
Here is a hand I do not recommend for an overcall:
Opening bid by right hand oppenent is one club. Do not overcall one diamond with this hand. Your stength is not in the diamond suit, so it would be misleading to partner. Moreover, it does not interfere with the opponents. They will have no problem finding a major suit fit if there is one.
Recommendation: When opponents open one club, do not overcall one diamond unless you have an opening hand. Make sure you discuss this with partner when going over your convention card.