There's no doubt that potatoes raise blood sugar more and faster than almost any other food, so keeping portion sizes small is a good first step. Also consider substituting vegetables which are lower in carbohydrate.
Comparing Root Vegetables
Carb comparison of potatoes, sweet potatoes, turnips, and more.
No, really, cauliflower can be a great substitute for potato. I have recipes for mashed cauliflower, cauliflower "potato" salad, and more. These recipes are requested among family and friends, even those who think they don't like cauliflower. (When you get to the link, scroll down to see the recipes.)
I like this vegetable a lot. You can pureed it like mashed potatoes, make "potato" pancakes...even chips! It's good in stews and soups, too.
I have been hearing about people using jicama
in place of potato, but I confess I haven't yet tried cooked jicama. This post in our low-carb forum describes one reader's experience with it.