be as detailed in the spec as you can, therefore no misunderstandings and the quote you get is more realistic.
Overestimate on electrical because extras seem to be relatively more expensive than a big spec on day 1.
Give yourself the odd weekend off, it can be a bit of a 24/7 preoccupation and you dont want to end up burned out. Pace out stuff that can wait, dont kill yourself painting the whole house if you dont need to, just lash on the white undercoat around where the skirting boards & architraving (door frame) will be, loadza time to do the rest after you move in. Cover stuff like window baords with plastic and/or tape, a lot easier to prevent mess than clean it off later.
Watch what is going on daily, tradesmen tend to go the easier route for them, as opposed to what you want. So be vigilant because if you dont catch it early on it might be "too late" - i.e. too much hassle for everyone and maybe more cost for you.
Be straight with tradesmen, if you get decent ones then keep them happy - dont keep them waiting for cash. It is possible to end up with a good relationship with them which can have benefits for you as well.