well, Fulla is right generally, but I do think there is a difference betwenn 10 and 14 team leagues!
10 team leagues are way easier to draft, as there is plenty of talent available also in the middle rounds.
14 teams makes it a little trickier. Generally the rule take the best player available also stands here, but you have to take care, that you dont get lost on RB or QB position after 4-5 rounds.
I would say, try to have at least ONE RB after two rounds and one QB after 4 rounds, then you shouldhave filled these two positions at least with one player. from then on take the best available WRs/Rbs (there wont be much left....so better try getting another RB at least in round six). So after six, if your roster looks like: 1 QB, 2RB and 3 WR it should be fine.
Remember, 14 teams means, if every team has 2 RBs, there arent much starters left there, so you have to look out here, to get a second starter relatively earlier. In smaller leagues you will get at least some less rated RB-starters in the 8th-9th round.