Until a year ago or so, the standard strategy was to go for a Running Back in each of the first two rounds. That has changed. However, if you can pick up two RB's who will not be part of a RB committee, take them and be happy. Teams featuring one RB have decreased and the move toward RB by committee has increased.
My preference this year has been RB and WR in the first two rounds. Wide Receivers are less susceptible to injury than RB's. Picking up a top notch WR with one of your top two picks is a good idea --- if the draft flows that way for you. If a top RB or QB is staring you in the face, take him and get your top WR later.
Unless you land a top QB in the first three rounds, you are typically better off waiting to grab your QB in the middle rounds. Stay focused on nabbing top talent at RB & WR.
The Tight Ends will start to go off the board in the 4th round or so. Just like QB, if you can get one of the top tier TE's, go for it. If not, the difference between the 5th best TE and the 10th best TE is marginal --- so wait until the later rounds to fill this position. Again, focus on beefing up RB & WR and getting your QB.
Defenses usually start going off the board in the 8th round or so. I typically wait another couple rounds before selecting one. Defenses are often unpredicable from year to year so don't use an early selection on last year's hot D.
Kickers go in the last round, maybe 2nd last. While kickers will contribute substantially to your team, the difference among them is typically not that great. It can also be unpredictable since kickers are a product of the opportunities afforded them by others.
If you're new to Fantasy Football, you probably will not be playing with IDP's or Individual Defensive Players. The IDP aspect is a favorite of mine but is discussed in other articles.