It's a misconception that you need to sell visual product to use Instagram for marketing.
There are lots of brands killing it on Instagram with things like:
You can even measure the impact of your Instagram efforts with these tools:
To add to Bruce's great answer:
1. Use hashtags in your photos
Add 1-2 relevant hashtags when you post photos -- it'll give you more visibility in the search.
2. Connect all other social channels
Don't forget to connect all your other social accounts to Instagram -- so people can reach you there from your bio.
3. Post quality, personable photos
One thing I've noticed is that the most popular brands aren't using professional equipment to take their photos. The photos are of quality, but taken with a normal phone camera to be more personable.
4. Write short, concise captions
A picture is worth a thousand words, but a relevant caption only enhances your communication.
5. Tag people
But don't go overboard. Only tag the actual people in your photos. This makes your brand more personable.
6. Like photos and leave comments
Be on the look out for photos that are going viral which relate your own niche and message. Like them and leave a memorable comment.
7. Respond to questions
Respond to people when they leave questions in your photo comments.