Yes, among the first things to do is get pre-qualified for a loan, but it is not the first thing to do.
You first have to think through whether you're ready to buy a house, because it is a commitment. Many people 6 or 7 years ago thought they would buy a house and then just sell it at a profit in a few years. That didn't happen. They either took a loss or are still in it. It is a commitment when you buy. You may be there a lot longer than you thought.
You should be comfortable with your payment. Look at your budget (most young people don't have a budget - they just spend 'til they run out). You know you can use your current rent for a mortgage payment and if you buy a house, under current Federal law you can deduct your mortgage interest and real estate taxes. Deductions result in a refund of your tax rate times the deduction (give or take) - ask your tax advisor.
So, with your current rent plus a reduced tax burden will that cover your monthly payment or will you need to spend more money each month? Do you have a car that is going to need to be replaced? Do you have student loans that will come due? All these things are important and known only to you at the moment.
Figure out how much money you can come up with reliably each month.
NOTE: lender will often limit the amount you can spend each month on your mortgage payment to about 41% of your monthly gross income. But that 41% includes all your debts, like student loans, credit card payments and so on.
Now, think about what kind of housing you want. Is a single-family with a white picket fence in the suburbs your style, or maybe a 3-story townhouse near the arts district, or maybe a condo by the lake? How big should it be? How many bedrooms, bathrooms, garage places, and so on. Will it need to be larger in a couple of years to accommodate kids or more junk, or maybe it should shrink. Shrinking is easy; expanding space is not.
Where do you want to live? How long of a commute to work and other relatives and church and shopping et cetera? A Realtor can use your help in finding the house you're looking for if you have already thought these things through. You can be flexible, just not clueless.
Now, go to a lender and ask to be pre-qualified. A conditional qualification means you have not surrendered every single bit of information about your life, but it appears you can get a loan, or not, of a certain size.
A pre-approval requires your file be submitted to underwriting for evaluation. That's right. A conditional approval means you did surrender your W-2s, tax returns, have your employment verified, pulled your credit report from all 3 bureaus, and so on. Don't let people tell you you're approved when they mean "pre-qualified" - they are different.
Those loan officers should be shot if they send you a letter using the word "approved" if they haven't received your tax returns and all the other stuff from you. A guy cannot pre-approve you in an hour. It takes a few days - maybe the next day if it's not the last 2 weeks of the month.
Is it possible that someone would spend money to pull your credit, analyze your file with all your W-2s and 1040s and so on, submit all that into DU or LP and have underwriting look at it, all for free? Get real. Okay, some will, because they want you to come back, but don't count on it being free, unless it's just a pre-qualification.
Just a caveat about adjustable rates: don't. A loan that can change by 1% every year may sound reasonable to some regulator in Washington, but when your mortgage payment jumps by 13% on the principal plus interest, you'll realize what adjustable rate actually means. Starting at 4% the cost per thousand of loan is $4.77 while a 1% rise would put it at $5.37 - 12.6% more. And it can do that every year?!?
At this point, if your eyes haven't glazed over, you're ready to research the geographic areas you think you want to live in. A Realtor can definitely help you here. You'll already know how much you can spend. Also, you'll know if there are things on your credit report that you need time to fix. Work with your Realtor. Don't drive around and call each Realtor on the signs you find - you can, but remember they by law work for the seller, not you. They can't lie to you, but who is going to help you and advise you, if they are working for the seller?