what i do is this, i put a heavy bar on my back and i try to sit down without falling over, then i try to stand up, again, without falling over. If i can do this 7 or 8 times i try it again with more weight. But thats just me.
Nice to see that no part of your reply answered the original question that was asked, actually quite suprised as this is not even close to your normal level of sarcasm, are you feeling ok?
I would assume UE that screwing your heels in is second nature to you? you might be suprised that many people dont realise this is as important as it is, and for some it makes a big difference to performance so explaining it in more detail helps!
personally i didnt even consider doing this, and hadnt seen much mention of it until recently, and i must say it definatly makes a big difference to the squat.