
Your loan officer is the person who will help you navigate the process of getting a mortgage loan. He or she will help you complete your loan application, gather the necessary paperwork, and explain your options. The loan officer will issue a pre-approval letter, lock your interest rate, and keep you and your real estate agent informed throughout the process. Your loan officer is the person who should hold your hand until you get to closing.
So how do you know if your loan officer is any good at what they do? How do you know they have the experience necessary to do their job?
You can start by talking to your friends and family in the city in which your house is located (or the city in which you want to buy a house). Who have they used? What was their experience?
Also, ask your real estate professional who they would recommend. Don't ask for the same three names they hand to every customer. Who do they know personally? Who have they successfully worked with in the past? Who would they really recommend?
You can (and definitely should!) also determine a lot about your loan officer with a little online sleuthing. Most* mortgage loan originators in the US have to be licensed. We're required to put our license number (or NMLS number) on EVERYTHING - email signatures, business cards, loan estimates, and web sites. It won't be hard to find. Mine is at the top and bottom of every page on this web site.
Pro Tip: The NMLS assigns license numbers sequentially. So the smaller the number, the longer the loan officer has likely worked in the industry.
Armed with an originator's name and/or license number, you can find out how long they've been in the industry, how long they've worked for their organization, and what kind of position(s) they've held. Just visit the NMLS consumer access database.
Check out these examples.

Take the person above. They've worked as a loan officer for two years. Prior to that they worked in marketing, managed a manufacturing team, and sold plumbing supplies.

Compare the previous example to this one.
Or to this person.
Who would you want managing your loan process?
You can also check out the company for whom the originator works, make sure they're licensed in your state, and review any regulatory actions against them.
* Loan officers who are employees of banks do not have to be licensed. They will have an NMLS number, but they are "registered" instead of "licensed." Registered bank loan officers do not have to meet the same testing and continuing education requirements as licensed loan originators. In fact, they don't have to meet any testing or continuing education requirements other than those required by their bank. Yeh, it's weird. But that's the law.