How about:
(1) Have a time limit on the offer, e.g. Summer Special - 25% off all Nails and Waxing Treatments until 31st August 2009.
(2) State that this offer cannot be used in conjunction with any other offer. So the 3 for 2 on all Waxing treatments could then not be used with 25% off as well (although the 3 for 2 could work out better value if the 3 treatments chosen were close in price - if all the treatments were the same price, then the client would save just over 33% by choosing the 3 for 2 offer).
That way, you could think about initially printing just enough leaflets to cover you for the next few weeks; once September comes, if you are still short on custom, you could run an Autumn Special promotion, e.g. Half Price Rebalance with each set of acrylic nails if rebalance done within 3 weeks of initial application. Or Free Waxing Treatment for the host of a Waxing Party if there are 5 guests or more (that would be a good one for getting more people to try your waxing service).
Or, think about using your existing spray tanning service to entice people to try other services, e.g. Get a Voucher for Half Price Nails with every Spray Tan.
Or, introduce a friend to our Waxing service, and get 50% off your next treatment.
So, that way, you are only giving your best discounts to people who are actively helping you build your business by introducing new custom to you.
I think you'd be better doing something like that - i.e. thinking carefully about how you can grow the business through canny use of special offers - rather than just offering a blanket 25% discount to everyone. Make your clients work for you, rather than risking them take advantage of you!