I used to think you had to go and hit the twisties to scrub 'em in - how ironic - leaning the bike over onto the new bit of tyre that slips, so you don't slip!!!
But since then I've found that a heat cycle or two just from normal riding cures the tyre and sets it on its grippy life.
Always show caution until 50-100 clicks has been covered - but the heat cycles should do the trick.
Some folks in the states use a chemical (can't remember which one), this is unnecessary. Just treat 'em like it's raining for the first 100 clicks and you should be right.