Regarding timelines, just bear in mind that is better to be ROUGHLY right that EXACTLY wrong.
As it has been said already, always give yourself a considerable buffer beyond the time that was estimated and that you ought to try to breakdown development into cycles, since you'll get better estimates down the line, given you also have more information available to work with and base your new estimates on the previous work and how it went (it's only indicative... but better than nothing if you are cautious with it)
Accept that tasks won't take exactly the time you think they will. Break them down as much as possible and, if your current methodology allows you, only break down the tasks you'll be working on in the next few weeks (I know, you have to break the others too to get an estimate for the whole project, but honestly you'll be doing nothing more than guesstimates if you haven't started coding the very first few, do it but know that the more further away from the present you estimate, the worse the worse they'll be).
Another golden rule is never to let business estimate times for development tasks. Developers should be estimating time for the tasks they will be doing. They might be optimistic of pessimistic or roughly right, when you come to know them, prefer the last two estimates (in worst case, it's better to underpromise and to overdelivery and you can always help the over pessimistics to tune their estimates). This might be difficult and business people may not always (if any time) buy it and can impose hard deadlines... Just make them aware that there is a risk that they might be entering in technical debt, which as any debt will have to be paid sooner or later, whether that means that a new feature will take longer because the code is a mess or because bugs will pop up since there wasn't time to have proper automated and acceptance testing.
Books I found useful, although I'm not a CTO myself (a bit methodology dependant, sorry):
The Art of Agile Development (O'Reilly)
Agile Estimating and Planning (Prentice Hall)