SMS wrote:
We have either a mouse or a roof-rat running around inside the attic.
You can hear him (or her) mainly early in the morning.

I set a trap with peanut butter on a piece of bread as the bait. So far
no mouse, but it's only been an hour.

Any other advice on how to catch him (or her) would be appreciated.

The trap I bought is the following:

"http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=94397&CategoryName=&SubCateg oryName=".

Give it time - it could take several days - but if it is only a mouse,
tripper will probably not be set off. I've had them eat peanut butter
out of regular snap traps.

If it is a squirrel, after you get it, seal openings. One of my son's
had a squirrel die in his chimney and it cost several hundred dollars to
have removed and repairs made. I get mice in attic sometimes and I just
toss poison bait up there. If they die, I do not smell them.