If you're on your own in your garden or pitch, get something to run at ( I used a bin as it is roughly the size of a player about to tackle) then just practice side stepping it. Remember for it to be successful you need to draw the player so run at the inside shoulder (one side of the object) and then just side step past when you get quite close :) If you have a friend who is willing to stand around for a while, get a cone (or make a mark) and make them stand there. The rule is they can't move their feet but they can move their arms and lean, what you then do is run at them and try and get past without them guessing in time where you are going (obviously they will probably touch you most of the time but that is because as they are stood up it's easier to re-act to the change plus their arms will be able to brush you but they wont be able to do that in a tackle!) To mix it up throw in a couple of dummies to get past too :)
Play against bigger players, when theres a 20 stone samoan about to tackle you you'll soon learn to step them
play more footy and run angles then straighten up always works
Jake's got a good answer, but you could also do agility ladders. Personally, thats where I find most of my footwork comes from. Practice things like the Icky shuffle (google it) and crossovers. Practicing on a cone, or something will work, but to train, ladders work that repetition and muscle memory that will make it second nature in a game.
