Small presses, when they have the money, are more likely to spend it evenly on promotional efforts for all of their titles. Ultimately, you may have to make a judgement about whether you can depend on the publisher's publicity department to do a good job. Find out if there is a budget for promoting your work. As well, certain editors have more connections than others with book reviewers, columnists, and commentators. If you don't think your publisher can promote your work dependably, you may want to hire a freelance publicist, promote the work yourself, or find a workable combination of all three methods.
Commercial distributors provide publishers with marketing and sales services.
When a promotional campaign works well with distribution efforts, copies are sold to libraries, bookstores, book clubs, and catalog outlets. If you are lucky, your publisher will promote your book with a lavish advertising campaign and distributors everywhere will pick it up for sales to libraries and bookstores. If you are the average writer, your publisher will probably spend a small amount of money to promote your work and, especially if you are just starting, you'll end up selling most of the copies yourself. The press print run is another consideration. Especially if you pay someone to print your work, you should find out who owns or has rights to extra or unsold copies.