"Tactical Espionage"? Have you been playing Metal Gear Solid 2 lately? Hm. Can't blame you for that!
Anyway, I could give you one general rule that applies to every character: Never Stop Moving. I think it's a good idea to Super Jump around the arena, to make yourself harder to hit, but it can be turned against you if you're not careful...to Super Jump, hit Down, then Jump!
Second universal tip: Don't Waste your Tags. I see players use up all their tags in the first few seconds of the match, and it hampers them for the rest of the game. Remember to use them in moderation! You'll be hurting if you don't. To Tag in your helper, press Mid Punch and Mid Kick simultaneously.
Last tip: Learn the moves! There are several fan sits out there with everything you need in this department. So do your homework before you play, and remember to practice these moves in the Practice mode just to be safe.