Here's a couple things I do:
(1) I create a budget every month. I have a spreadsheet in excel that does the math for me. So, every week I put at the top of the column what the total income will be for that week, and then I go down the column and insert what the expenses will be for the week. If my income exceeds my expenses, then I put the excess in a separate column and call it the "vacation" column. At the end of each week I go back through my expenses to see if I controlled my spending. If I did, then I put that vacation money into my savings account. It's good to have it in the checking account in case I need it for something. But, it's also great incentive not to spend it knowing that if I don't spend it, I get to put it towards Disney.
(2) I have a program on my checking account that every time either my husband or I use our debit card, $1 gets put into the same savings account I put my vacation money in at the end of the week. Usually it ends up being around $100 a month.
If you even leave as little as $50 at the end of each week for vacation and you do that debit program with your checking account, you could end up with roughly $300 each month. By the end of the year, you're looking at $3,600.