One of my websites, www.cadenzaweb.com
generates about $3200 in sales a month, but profits are slightly below $2000.
The biggest tip I can give is be honest and upfront with your customers. I always say that trust sells products online, not ad-copy. Trust is the most important sale you'll make, but is always the hardest to earn. Make sure you have a way for all your clients to connect with you directly. Toll-Free numbers are a must. Answer every email personally, and take interest in your client, and their business. Keep in touch with them, even if it means initiating the conversation.
The best advertising will always be Word-Of-Mouth advertising. Make sure you clients know that if they are happy to tell their friends.
Testimonials, Testimonials, Testimonials.
Become an expert in your field. Strive to learn everything you can about the services you provide. Never stop learning.
Don't undersell yourself. I often see people competing for the lowest priced service. Fight for the highest quality customers instead. 9/10 times, the highest quality customers wont be looking for inexpensive services.... more profit for you.
Keep track of every aspect of your business on paper, or in the computer. I use quickbooks to manage everything. Track your PPC campaigns, ROI, SEO etc...
Many young business's fail due to a lack of profits, obviously. Be thrifty with your spending. Don't hire someone to do what you can do yourself. The less you spend, the more money you make. Now, there are obvious exceptions to this, like Hiring and SEO if you don't know what you're doing well enough, and hiring a graphic artist to design a logo, if you can't draw to save your life.... etc...
I can't tell you how many times I've seen people over pay for hsoting. Now, hosting is vital to your business, and shouldn't be something you skimp on. However, I get people all the time who tell me "I got a sweet deal on webhosting!! 10 gigs of space for $50/mth!!" Etc... In reality, you most likely won't need 10 gigs of space... don't pay for what you don't need. If you only need 100 meg, don't pay for 10 gig!! That's a huge amount of your profits out the window, especiallly for startup companies. Buy from a reputable company, and buy what you need. Trust me, they won't complain if you want to upgrade later.
If you are serious about making money online, you have to treat it as your job. Devout a few hours everyday toward it, and schedule what you have to get done that day. Always plan in promotion, email time, etc... I see many people who think they can set up their website, and let it run itself. Never happens that way. People who make it big, work harder and smarter than anyone else. Eventually, you'll get to the point where your business becomes your full time job. Then you can devout more time to it, and become more succesful.
This thread so far seems to be very money motivated, but remember that money is not only reason to work online. Money is nice, but if you focus on enjoying what you do, working for yourself, and having the freedom to make you're own schedule, then you are in the right business.
Remember, There's no such thing as luck online, only hard work, and persperation pay off. I'm very interested hearing what others have to say. I'm exhausted, so I'm out. Hope I have been of some help.