Aikido forward roll
Stand with your left leg in front and your right leg behind you.
Lower yourself to one knee, with your left knee raised and your right foot behind you. Try to keep your right toes pressed to the ground, instead of the top of your right foot. This is referred to as "live toe", and will become important for more advanced ukemi.
Rotate your right leg so that your foot ends up behind your bottom.
Lean your left shoulder down obliquely in front of you.
Place your left arm, slightly rounded, in front of you with the blade of the hand towards the ground. Round your right arm down to almost touch your left. They should form a circle.
Turn your head down and look behind you, under your right armpit. Your head will maintain this position through the roll.
Slowly overbalance yourself forward, until you lose balance. The first part of your body to touch the ground should be your hand blade. You will be rolling from the blade of your hand up your arm, across your left shoulder, and onto your right hip. It is thusly important that your left arm be strong enough to support your weight, but not locked out or rounded. It takes practice.
You should return to a position similar to that in which you started- with your left knee up and your right down.