So you think you're pretty handy, huh? You have fixed some plumbing problems and serviced your air conditioner and now you're ready for a larger project like laying tile, putting on a new roof, or building your own fence. More power to you. Be careful! Sometimes DIY projects gone bad can cost more than just hiring out from the start.
Practice Makes Perfect
Before entering into a project, it may be a good idea to take a trial run. Never try out a new skill while working on a permanent endeavor. The end result could be disappointing, which means you have to tear out and begin again, or call a contractor to get you out of a jam. For instance, when installing tile, buy an old table at a thrift store, lay down some guides rods (wooden dowels do the trick), and practice laying it before installing it. Or when painting rooms, start with the smallest area first to see how the paint color looks and to gain some hands-on training before moving on to the kitchen or living room.
Prepare to Prepare
If tackling a large project (building a deck, replacing a roof, painting an interior) apply the brakes before your begin. Preparation saves you tons of hassles: trips to the store, additional labor, and costly replacement parts. First, if installing a new addition, check local codes to see if it's legal. Then, draw up plans and don't rush. Take a few weeks to think about the project. Let your ideas percolate before going to the hardware store. Then make a thorough list and buy in multiples when it comes to brushes, rollers, and other small items. And always consider safety beforehand: shutting off electricity or waterlines, wearing goggles and boots, and making sure the area is barricaded from passersby.
Design on the Inside
When it comes to interior design, there seems to be a lot of strange rules. And design shows on TV always turn a boring room into an extravagant work of art. This is a great idea but sometimes the end result looks worse than the original. There's a difference between works of art and trying too hard to be trendy. And sometimes luxury remodels, (steam showers, heated flooring, or built-in appliances) are so expensive you won't get a return on your investment. Instead, stick with the basics, such as painting, flooring, and cabinetry. Also, while redecorating, consider your own personality and trust yourself. It's your mortgage, so let it be your style. And if undecided, then let the decor reveal it: oftentimes, when re-selling property, the best choice is to stay neutral. But, in the meantime, if you're living in a house for years it'd be a shame if it never felt like home.
Find a Support Group
Never face a project alone. There is a certain satisfaction in doing a job yourself, but most situations call for a crew. Whether it's moving, clearing the garage, or painting a house, never feel you have to take it on single-handedly. Most people don't mind helping, as long as you return the favor someday, and it's a great way to earn a new friendship with a neighbor. Plus, more hands also means more heads: it never hurts to have additional advice on how to complete a project. As for pay, friends and family are great forms of cheap labor, so treat your impromptu employees well: afterwards, pay them with a pizza, beer, or small gift (cookies, gift certificates, or a promise to help them when the time comes).
Know When to Fold Them
The sign of a true handyman is knowing when you're in over your head. A do-it-yourselfer who is able to ask for help obviously values their home over their ego: it's the sign of a true professional to know when to say when. If things get too big, complex, or demanding, call a service professional to help with the project. There's no shame in it, especially if you consider the money and time you'll actually save in the long run with proper installation or repair. However, this doesn't mean you can't help. Before the experts arrive, you can still remove old parts, demo preexisting construction, and prepare the areas as best you can to help the project go quick and easy. 
Marc Dickinson has worked in both the general contracting and landscaping trades and is currently a home improvement freelance writer with over 300 articles published.