I believe it really depends on which character you're talking about. Characters who specialize in long range are best handled with a face-to-face approach. Get right up on them, shield when needed, then counter. Close range characters can be sniped from afar after blowing them away from you via dsmash, dtilt, or something else. Since Yoshi's more balanced (as in, lack of surprisingly broken areas) than most characters, knowing your opponents' strengths and weaknesses will reveal your strategies to you indirectly.
My example is my tactics vs a Fox. Though he's usually in my face drillshining or uthrow-uair (where the second hit can be avoided by DI'ing repeatedly left and right.....thanks Toasty! :D ), when you land a throw or a dtilt, you can take advantage of the stall time via combo or tech chasing. In other words, charge in knowing what may happen, then stay close while trying to set up for wreckage is my strategy vs a Fox. But, that's just the Foxes I've faced. It's best to find out for yourself, IMO.
