check all your pieces against forks, being en prise, being pinned, discovered attacks, double attacks, on every single move before pressing 'submit'. also check for simple mates. not dropping pieces should get you to 1600.
don't do positional sac's, they'll just cost you material. only sac when you're absolutely sure you'll mate or get the material back.
don't attack before you've developed all your pieces. unless you win material.
be as agressive as safely possible. move with a threat if possible.