If the diamond quality is vastly better than the clubs, then open 1D planning on rebidding clubs; otherwise open 1C.
If the club quality is vastly better than the diamonds, then open 1C and plan on rebidding 1NT if partner responds 1H; the club suit can be expected to run in such a situation, and so how much trouble can you get into in 1NT.
Remember that if partner passes a 1NT rebid by you this shows 6-9 points to go with your minimum opener. If you can't make 1NT on power and the club suit, the opponents can probably make at least 2S (or 2H!); going down 1 or 2 undoubled is a win.
The big misconception newer and intermediate players make is thinking that 5-card suits, by either responder or opener, are a preferable rebid; this is untrue; rebidding a 5-card suit is a desperation rebid to be done only in dire circumstances, or to reveal a 5-5. Both opener and responder should try keenly to avoid rebidding 5-card suits, and save such rebids for 6-card suits. Partner will preference back with 3-card support unless her hand is strongly no-trumpish, at which point the 8-card fit can be revealed.
In regards to Rud's statement about opener's raise of 1M with 3 card support; I have always felt comfortable raising partner's suit with 3 and a side singleton. If partner cannot handle the occasional Moysian fit, I find another partner. (And I never have difficulty finding partners.)