Once in a while, I have lunch at a market near my home. There's a struggling greasy spoon that has changed owners several times. I've never ordered from the greasy spoon because their menu looks like this:
spaghetti
chicken

• burgers
• sushi
• potstickers
• meatloaf
• pasta with your choice of 10 sauces and three meats
• teriyaki with your choice of two carbs and three meats
• pizza
• all-day breakfast
• salad with your choice of three meats
• and so on

The greasy spoon has pictures of all the foods hanging above and around the counter. Some of the food actually looks pretty good. But I've never ordered any.

Why? Nobody can possibly do all those things well. The greasy spoon has failed to specialize. As a result, my trust in their abilities is eroded. If they had a tight menu, I'd probably try it out. But the laundry list of food options suggests to me that they don't even know what they do well.

As I mentioned in Do you do "X"?, it pays to specialize. By keeping a tight rein on your business offerings, you'll be in better control of your business. More importantly, clients will be more likely to see you as an expert.

What do you do well?