You know with Broken Steel came those perks which can change your characters alignment.  If I turn my good character evil via the use of these would I get the achievement for 'reach level 20 with an evil character.' Or do you have to be evil the exact moment your character hits 20.

Thanks for any help you can provide.

I would guess that you have to use the perk at lvl 29, since you traditionally level up and then select a perk.

you have to be good or evil at the point that you reach those levels.

Ahh, cheers man. At least I can use them to get the alignments at 30 achievements easily.

If you are trying to get the achievements for all three karma levels, all you have to do is create a save file right before you hit level 20 or 30.

Then go ahead and level up to either 20 or 30.  You won't get the achievement until after you decide which perk you are going to choose.  So if you choose the bad karma perk, you'll get the achievement for reaching level 20 or 30 with bad karma.   

After you choose your perk and you receive the achievement, go and load your save file that you made.  Kill a few guys and level up.  Then choose the other karma perk at which point you will receive the achievement for reaching level 20 or 30 with that specific karma level.

Then load the save file again, rinse and repeat.  You can literally get all three of the level achievements at the same time.  In turn, saving you a ton of time.  I love this game but I do not see the point in going back and playing this game three times over.  Especially when one playthrough with DLC included can run you over 50 hours if you were just worried about leveling. 

I have all of the achievements for this game and way over 100+ hours of gameplay.  And thats without going back and playing through the game 3 separate times.

This method was a little more tricky before Broken Steel was released.  You literally had to create save files at levels 7, 13, and 19.  Also, it was much easier if you played through with the highest karma level.  So all you would have to do is go to Megaton, kill some friendly's which would take karma away and then leave once you have aquired the specific level of karma.  Then go into the wastes and kill some Mutants for experience until you hit level 8, 14, or 20.  Again, rinse and repeat for the other levels of karma.

Tricky but nowhere near impossible.  Hopefully you made a lot of save files like myself.

I found It easier to start a very evil and work my way up by giving purified water to Micky in front of megaton it only takes like 14 waters to get you from very evil to neutral then 14 or 15 more to get you to good. 

What PIG20 said is the best course of action is you must have these achievments.  I'm level 30 with 136 hours of play and the only time I used that method was at level 30 with the perks which means I'll probably run through the game reall quick with another character.

Just take the Here And Now perk when you reach level 29. As soon as you do, you'll be at level 30, and you can do all those Karma perks.