Assumptions

Never assume your system is compatible with another one. Test it out. Test the actual environment out. Simulators are great, test environments are great, but test the actual environment too, avoid the regret and embarrassment.

Hiring software developers

If you are going to hire a full time software developer make them write some code right in front of you. Make it something simple. How about one recursive function. If they can't write one recursive function in front of you, why are you hiring them? You would be amazed at how many developers come to an interview and are frozen in terror at the prospect of writing code. Hire the guy that jumps at it and has an obvious passion for his craft.

Software Estimation

I am currently studying software estimation in depth.
This may be the hardest part of software development in my opinion. Never trust a software developers estimates. I use the double it and multiply it by three rule which is much more accurate. Take whatever estimate the developer tells you, regardless of how they derived it, double it and multiply it by three and you will have your real ballpark estimate.