1. Focussing on the product and not the solution it provides
Often startups are so consumed with the product they are building that they forget that it is only useful if it solves an end users problem.
2. Functionality for the sake of it
Too many features from day one means you never get to launch. MVP (Minimum Viable Product) should be the mantra of all Tech startups to avoid getting beaten to the post or never shipping at all!
3. Being too, secretive about what they are doing
There are plenty of ideas out there, nobody wants your idea they want to be part of the finished product. You want investors, you want advocates, you want people to help you succeed? Then tell them everything you can about what it is you're doing. Playing your cards too close to your chest will only leave you alone in the battle to launch.
4. Build it and they will come
Oh no they won't. You need to scream from the roof tops all through development all the way into launch and beyond. It's a noisy world out there make sure you get heard.
5. They don't write enough
If you can't write, learn to write, if you haven't got time to write, dictate or record YouTube videos. You should take every opportunity to write about your experience. People will love to hear your startup story making it far easier to get your product to market. You never know you may even become famous by accident along the way!
6. Borrow too much or give too much equity away
Are you sure you need that money? Every bit you borrow or every share you give away cuts into your potential. By all means don't cut yourself short for the sake of it, but it is amazing how far you can get under your own steam with a bit of inginuity.