Never Leave Your Tower!
I know everyone knows that defending towers is a vital part of the game; I'm addressing the players who will vigorously defend a lane for 3 minutes, then turn and go shop/ heal, without letting the roamer on their team know that their tower is undefended.
This is such an important part of the game, especially early-game Cataract 3v3, and yet it is a mistake I see made all of the time. (Also, although I am sure it is common knowledge among experienced players, it is a topic I have not seen discussed on these strategy forums- unless I missed it somewhere.)
There are plenty of strategy guides that will point out how to use the towers for protection and to help you farm when you can't hold the flag against a mismatch. Good players (I am thinking of Teseer's TB here) use the towers like a car wash, buzzing through their range when covered in a filth of Spirits or Night Walkers or other experience-deprived annoyances.
BUT, you have to look out for your tower too! He is your friend. He spends the whole game watching your back. Don't walk away from him when he is staring at a minioned Erebus or Oak, a Queen, a Rook, (or any DG for that matter) with no place to go. When you come back, he won't be around to play anymore!
Don't walk away from your tower just because you have been beaten back, are at half life and OOM. Early game, even a wounded DG in the shadow of his own tower is a threat. Don't leave until you let someone know you have to, and they come and take your place. Don't announce "shop" when you are already halfway there and at the same moment I hear our gold-side tower come crumbling down.
If you have been beaten back, stand there, out of spit range, and if they come up to attack the tower, fake charge them. They may see that you are low on health, but they don't know if you still have one Fireball, or Penitence or whatever left. They also can't see much past you, so you may not be alone. Against most players, most of the time, this is enough to make them back off, and give your tower a chance to heal.
No item at the shop, no citadel upgrade, no full-mana bar is worth losing a tower over. Communicate! Say, "Hey I'm OOM and need to shop. Can you come guard my tower for me? I'd really like it to be here when I get back!"
