Don't alter your routine - you'll need to find a way to carry on your affair without staying late at work, for example, if that's not something you ordinarily do. Obviously, a paper trail will raise all kinds of red flags. Pay for whatever you can in cash, and make it the responsibility of your lover to pay for hotel rooms if need be. Don't fish off the company pier - in other words, don't take your lover to your home or frequent haunts - there's too much risk involved. Other evidence to be vigilant about include birth control. It goes without saying that you should be using condoms with your lover to protect against sexually transmitted diseases, but don't allow your spouse or partner to find them, particularly if it's not the form of contraception that the two of you use. Finally, if you're not planning to leave your permanent partner, then keep feelings out of the picture. Break it off immediately if you think you're developing feelings or think your lover might be falling in love. Be prepared to face whatever consequences come your way if you cheat.