Ok, first of all -- you need to figure out where these buggers are gaining
entry. Trap, poison, exorcise, whatever -- until you figure out their point
of entry they will continue to be an ongoing problem.

Secondly, you need to identify just what your problem IS rather than making
an assumption. Is it squirrels or perhaps rats or maybe even bats, cats,
birds, racoons, mice or who knows what? You should be able to make this
determination by first an inspection and then a trap, as well as once you've
found the entry point. If the activity in the attic is consistently
occurring, you can also try to videotape it and see what you get.

Once you know what you're dealing with and how they're getting in, THEN you
can actually deal with the problem. Plug their entry point then set out
some traps, see if you catch anything. If you have rats then pick up the
snap traps (good ole Victor Pest) and coat them with peanut butter -- set
them all about the attic, especially along the walls. You can use poison as
well but at least with snap traps they won't be going off in a corner to
die.

Another item -- if you have rats, then the live catch and release bit is for
the naive. It flat don't work. By now they've bred and had at least 1 full
litter which has probably matured and started breeding as well (assuming the
time of the year and weather is similar there as it is here). One year we
had a rat problem and did not realize it until they had set up a happy,
happy home -- when all was said and done, I stopped counting the dead at 72.

If it really is squirrels, then blocking their way in will resolve the issue
fairly quickly. Same goes for bats or other nocturnal types -- just be sure
to do the blocking when they're gone.

Good luck.

James