There is no real guide book for choosing long distance movers. A lot is affected by your gut instinct and your involvement in the research end of things. However, the more work you are willing to put into researching long distance movers, the more success you are likely to see come out of it. And in the end, you will have movers with great reputations instead of OK ones, and great services instead of mediocre ones.
First, ensure all long distance movers you research are both licensed and certified to handle long distance moves. It is common for companies to say that they cover moves over long distances, but many companies do not have the paperwork to back up their statements. A quick check into each mover will verify whether the mover handles long distance moves regularly or whether it has handled just one move over the course of its existence.
Second, ensure all long distance movers have good reputations. Look for anything damning or particularly negative about the long distance movers on your moving possibility list, including scoping out review sites and doing general searches using these companies names online. Find what you can about how others feel about these movers, including discussions of their moving capabilities, their flexibility, their costs, and their people and how well they are trained. Again, the more you find out about these places, the more well informed you will be in ultimately making a good choice in a moving company.
Third, check with the local better business bureau to see whether the long distance movers you are looking at are members. This should not necessarily be a deal breaker, but it certainly helps to have a noted member of an established and accredited agency that can vouch for its reputation. Ideally the movers will be embedded in some form or another in the local community, such as by participating in chamber events and sponsoring others occasionally. Affiliations with national and regional moving associations is helpful too.
Fourth, ask around. Do you know people who have moved recently? If so, did they use local movers or long distance movers? If it was the latter, learn from them the positive stuff about the companies they chose, and the negative stuff as well. By digging deeper, you are further solidifying your chances of getting a quality mover at a price that will not devastate you financially.