One suggestion I have read, if you are interested in making an effort to give more, is to take a look at your budget and see what percentage you give now (when my husband and I did this the first time, we were at under 1% of our take home pay, because we just had very little disposable income.) When we made our budget for the next year, we increased it to 1% (our financial situation had improved some, too.) The next year, we went up to 2%. Our goal is to eventually give away at least 10% - probably 5% to our parish, and 5% elsewhere. But we started much, much smaller, and gave away time when we could, instead.
(Edited to add: And even though we now give more, I still think it is our time that makes the most difference!)