1. Whatever you do, DO NOT tell her that you could/would marry her if you weren’t already married. Whether you mean it or not. Cos she might start to get ideas and think there might be a potential future. Before you know it, she’s expecting you to leave your wife for her. Unless she’s a very mature lady and knows when you’re just trying to flatter her, or understands that you’re never going to leave your wife.
2. Do put her on a schedule so that she doesn’t expect to receive more time than she’s ‘entitled’ to. If two days/nights a week is what you can afford, set aside those two days clearly and religiously. This will help you make ample time for your wife and it will teach side chick to be content with what she has. An added advantage is that she’ll start to look forward to those days and ensure that they go very well for both of you.
4. Do handle your marital business before you enter ‘side-chick time’. Remember, her own time is less than ‘wifey time’ (and rightfully so) so she won’t appreciate you further shortening her ration by having your family conversations when you should be spending time with her. If you need to check in with your wife, do it before, not during side-chick time, unless there’s an emergency. In which case you’ll be going home anyway. Note: Some side-chicks are actually able to deal with being present while you do family stuff. But most should be uncomfortable, because it’s a strong reminder of how wrong what they’re doing with you is.