hire your own home inspector, not the one the real estate agent recommends.
Just make sure your new home comes with a Bucket of Truth and a Hot Chicks Room; http://www.comedycentral.com/episod...izens-brigade-august-18--1998-season-1-ep-101
Upgrades inside the home are easier to do (in terms of not having to pay additional property taxes for an appraisal over) than the ones outside and tend to add more value to the home later.
Go for as big a garage as you can find. Look either for a half car extension or a full car extension over the amount of vehicles you have.
If you want a pool, buy a house with a pool. Don't put one in later. You'll never recoup the cost of a pool unless you can install it yourself. Then you might break even if lucky.
Don't be afraid to ask questions of anything. If you don't understand something, even if you think someone might think you are stupid for asking, screw them. ASK!
Pay attention to the homes around you. They reflect on the people that own them and more importantly, who lives in them. Crappy house, crappy neighbor. You're not just buying into a home, you're buying into a neighborhood.
I can tell you a mistake the seller of a house did when I purchased it.
His realtor made the mistake of telling me that he was in the middle of a divorce and needed to close in less than 60 days. At that point I had only looked at the property twice, liked it and made an offer. With time working against him, he decides to get into a bargaining war with me. He needed to supposedly close soon so I played hardball and refused to come up from my initial offer. With time on my side, I had no incentive to play his game and stuck to my price. I had other properties I was interested in and wasn't going to lose sleep if I didn't get this one. He instead wasted weeks negotiating with me and trying to get me to come up. Even his realtor started becoming uncomfortable repeating his offers only for me to reject them. I whittled him down 60K and as a consolation prize to him only went 1K above my original offer. Finally at 30 days to his supposed close date, he grudgingly accepts my offer.
I scheduled a home inspection and that came back with numerous things wrong with the place that I asked him to fix/replace or whittle further off of the price of the property. By the time everything was all said and done he had gone over his scheduled close date and had to take a bridge loan so he could settle his divorce, buy his ex-wife out from her share of the property and then close with me.
I can only assume that considering the fervor that he tried to get me to come up from my initial offer, he already lost money selling at my price. Then he had to make over 12K of repairs. Then with the interest and fees he paid for the bridge loan, well he probably lost a shit-ton of money. Maybe he was getting cleaned out in his divorce as well. He was so pissed off at the closing that he barely wanted to shake my hand. Whatever, thats his realtor's fault for letting his divorce date slip out. The moral is never let someone know time is working against you.
Using a real estate agent was a huge mistake every time I've ever done it. When I went through the process on my own, it was WAY smoother and WAY less costly. Regardless of the bullshit anyone tries to feed you, you and the seller are both paying for the agents.
I actually bought my first home without one and everything went great. I have no idea why I decided to use one on subsequent transactions, but I'm back to not being a dumbass. They literally add no value if you can think your way out of a wet paper bag. I guess I should also consider that some people are rather stupid and may need help from someone who is only marginally less worthless, but the fact that you're asking for advice up front means you're probably smart.
Also, SandEagle is right - don't use recommendations from an agent or a broker unless you independently arrive at the same decision through research or a recommendation from a person who doesn't have a hand in your pocket. Kickbacks for recommendations are both extremely common and directly in opposition with your best interests.
The best piece of advice I can give you is to relax and realize it's just a house. You've been fine so far without it and you'll continue to be fine if you don't get the one you think you really want. People get caught up in the whole ordeal and think they're missing out on a dream if a particular house doesn't end up in their possession. Don't let anyone pressure you into buying a house if you aren't 100.000% sure it's exactly what you want in the location you want at the pricepoint you want at the terms you want.
This is the single biggest thing I didn't understand until multiple transactions. YOU are in the driver's seat, but everyone throughout the whole process will be trying to drive from the backseat. If you don't like something, put your fucking foot down and make sure people know they aren't going to get their way. I'm being slightly abrasive about this for a reason; experience has led me to understand how the whole system really works. Almost no one involved has your best interests in mind, but they're all masterfully trained to make you think they really care and their number one priority is you. It's absolutely the opposite.
The only reason to have a real estate agent is if there are some non-disclosed liens on the property the seller is trying to hide. Or in Texas, if you are buying ag land that doesn't have all the yearly receipts, you could be screwed if you didn't catch that. With an agent, you put the responsibility on them to make sure all that is found out before buying.
Not really a mistake but ours was a new built and was not aware that gutters and grass and A/C was not included in the price.

I was living in Louisiana. I bought a mobile home.We're starting our preapproval process in the next week or two and I'm looking for some real world data. What better place than ATOT?
What do you wish you knew before you bought your first home?
Any horror stories?