I would be very careful about adding smoked malt - the flavors can become very overpowering very quickly. Unless you're looking for a full on rauchbier, I would be very sparing with smoked. Commercial smoked, maybe 5% tops, home it would depend on how long and such - short smoking times will have less smoke flavor, obviously, and vice versa.
There was an article in one of the magazines - Zymurgy or Brew Your Own - a couple years ago about home smoking. I would normally be able to put my hands on the issue, but they're all packed away in prep for my upcoming move.
Anyways, if you want to home smoke your own, I would probably do no more than a pound or so of malt, and probably not put all of it in, at least for a first beer.
Look for lighter flavor woods, cherry or apple, I would think - something like mesquite gives a super-sharp, phenolic flavor from what I remember reading.
You want to moisten the malt before putting in in, and spray it down with a mister a couple times during smoking. Low temp and far away from the fire is what you want.