For the homebrew scale hot side aeration is not an issue - it becomes problematic at the microbrew and larger operation as there can be a significant amount of wort agitation moving between tanks.
Basically dont introduce oxygen after your yeast can't be counted on to scrub it out (near the end of their feeding cycle). So for instance; if you are bottling then bottle conditioning - a little oxygen in touch with the wort is not a big issue, the live yeast will consume it. If you bottle out of a keg with a bottling wand etc, the oxygen has nothing to combine with except the contents of your beer (oxidized flavor).