Think this may have been posted but...
make sure your charaters are in the same area. now the char you want to buff, be on, then dissconnect. re-log and get on your main/alt you want to use to buff the alt. Now your toon should be sitting there for you to buff.
A few examples of buffs that would work well are:
Fortitude, Soulstone, BoP buffing crud (I just thought of using my mistle toe on my altslawl) use your imagination
ok for somereason i serious think this may have been posted. oh wellz, ill find out