How do I attach a toupee so it does not slide down?

It very much depends on whether you have enough hair left to adhere a clip to but the common practice is to either use a bobby pin to attach the toupee to your real hair underneath by sliding the clip through the mesh of the toupee. Alternatively you may wish to attach some toupee clips by hand (simple needle and thread job) to ensure the toupee will clip into your real hair. Another important factor is the fit of the toupee; if the fit is bad on your head it will never sit correctly.