I've done my share of starting up new companies, divisions, products, and even a spinout. The experiences have been tremendous and I wish I could say I handled all the lessons with grace but there were a few times when I didn't. That's probably my first thing I'd do different...
1. starting up a new business is incredibly stressful. Probably the most stressful thing you could possibly do with a professional career. Lee Trevino once said that pressure is playing for three dollars with two dollars in your pocket. That's exactly how I felt many times. Do your best to handle that stress with dignity and grace. Smile at the grim reaper (AKA VC's) and thank him for coming.
2. Don't waste a dime of effort developing partnerships. It's very tempting to say "hey, I've got a product that every customer so-and-so already has so if I partner with so-and-so, I will have thousands of customers!" Not gonna happen. Doesn't work. Get out and sell your product. Do it now.
3. You can't put all the sales responsibility on your subordinates. Maybe you're a geek and have never sold. Well go get some sales training and put on your sales big boots because if you can't sell, you're probably dead right now and just don't know it. Early customers want to see the genius behind the risk they are taking. And that's not some VP of sales you hired to contact 300 people a week. It's you.
4. New product features are rarely the answer. It's an easy trap to fall into. The reason things aren't selling is because they lack certain features so let's invest more. You can play that game all the way until you crash into the ground when you run out of cash. Get a product that someone is willing to by as is. And then go find more of those customers.
5. software-as-a-service revenue models take time. Not everyone is netflix who can charge a bazillion people $11 a month. It's a good business model but you need plenty of cash to get it to break even. The nice thing is that once you do, it's a helluva cash machine. Don't lose patience and stop selling after only six months. Have enough cash to give it a full shot if you believe in it. 18 months before you call it quits. Miracles can happen in months 10-12 but most people give up before they get there.