We had a rental loss of 14K in 2007. Because of our income level and exemptions we don't need to utilize this loss. I know we are entitled to 25K because we actively manage the rentals. I would like to carryforward this loss to 2008 and later.
Where do we show this loss on future tax returns. Do we have to amend the 2007 tax return?

This sounds to me to be a Net Operating Loss (NOL).

Filing a NOL is NOT something that any amateur should try, because it requires complex calculations involving previous tax returns. These calculations must be done manually, i.e. there is no tax software support.

You need to contact an experienced, competent tax professional who has in fact filed NOLs in the past to see if you are eligible for the NOL. Do NOT try to do it yourself!