BlinkXPoke wrote...
In sanctioned constructed is where I'm not so good since I wouldn't know how to beat popular decks or how to sideboard well, or even know how to build a sideboard. As I've said before in an earlier post about a tourney I went to, I just netdecked a sideboard for the infect deck I was running, with a couple of small innovations since my deck wasn't (completely) a netdeck.
Sideboarding comes from experience, testing and most importantly, research. The best way to do so is to (no joke) play the decks everyone else is playing, theorycraft all you want, unless you have hands on experience with the deck on both sides of the field, all you have is theory, no experience playing against, no idea how to go about applying hate or anything.
Easiest way to research for legacy or standard is forums and star city, usually you find a article or graph breaking down the meta (what everyone is playing) and you make your sideboard decisions as such.
Aggro and Control are easy to board (relatively speaking) once you get the hang of it, combo is tricky as you board based on hate, not based on the decks strategy, further, you also typically slow down 2-3 turns, depending on the combo.
If you can't beat 'em, join 'em..then beat them later ;).
(As far as budget legacy, I always recommend building tribal, they are easy to build budget versions of and the money cards they do use carry over between decks)