Basic drill help needed

Hi guys, have just started my AI training and had a very quick drill lesson last week, but its left me alittle confused - can someone please help :D
Its all very basic - but due to the speed of lesson, I didnt pick it up very well.
Could someone explain; stand easy, stand at ease and attention for me ?
I am especially baffled by the postion where your arms straighten behind your back - is this just part of the "attention" movement ?
Any help will be very much appreciated - dont fancy being yelled at, so soon in my training. I have no previous exp of drill - so need idiot proof instructions ! or a very good dvd !!
Blimey, a tough one to put into words! pictures and actual experience are the best forms of instruction.

Position of attention - Heels together feet at roughly 30 degrees apart (dont quote me on that). Arms tucked into side fist clenched thumb pushing down on top of fist.(try to get thumbs running down seams of trousers) Stomach in, chest out, head up and look proud!!

Position of ease - Feet shoulder width apart, hands cupped into each other (thumbs interlocking) somewhere on your arrse (depending on length of arms) arms locked out. you should see no air between arms and body

The stand easy - As above only arms are slightly relaxed. (Not resting in small of back as though you have 2 small wee cadets under each armpit.

When being brought to attention for the first time you should recieve the word of command squad/detail/platoon/troop/whatever................ command squad/detail/platoon/troop/whatever ......attention!!

The first bit is a warning to the squad that something is going to happen. At this point you simply brace your arms shooting your chin up (known as bracing up) before then coming to attention in a smart, soldier like and uniform manner.

My personal advice is to get yourself in front of a full length mirror and practice until your feet bleed! pain is afterall simply weakness leaving the body.

Hope this helps.
Thankyou - That is a great help to me. I shall indeed go stand in front of my mirror and practice until my feet bleed or until my flatmates think I have gone mad and get me put away :)
Thanks again - turning at the halt tomorrow !!