This a fairly easy one,but one tip-use good,high quality cards as they are much smoother than cheap cards and are well worth the investment. Go to Elussionist.com or just search google for some bicycle red backs,blue backs,black tigers or ghosts!(There are other makes but I prefer bicycle)
Step 1: The Grip
Hold the cards like it is shown in picture one.Keep the grip fairly loose and it helps if you have your cards on a grippy surface(a rug works well,or,if you could get a card mat but they are quite expensive).
Step 2: Dragging!
1.Start to drag the cards accross to your right appliying an even pressure to the cards all the way.
2.Now if you take your hand away your cards should be possitioned like this (pic 2)
Step 3: Flipping!
1.Put your hand under the far left card and raise it while pushing it right.This should flip the first card over a bit witch will do the same to the next card and so on.
2.This is the cards hallfway through them being flipped.
Step 4: Collecting!
1.You should now have the cards so that they look exactly like they did in step 2 picture 2 exept that they are now the other way up.
2.Get your hand under the far right card now and start pulling to the left to push all the cards into your hand.
Step 5: Squaring
1.You should have the cards like this now.
2.Square the cards up.
Step 6: Done-ing
Put them on the table or do what you want with your cards cos your done!!
Oh,and as Mr.Math says,practice,practice,practice!