This what I copied from another thread some time ago. Unfortunately I can't remember the name of the poster. Sorry 
to whoever it was but thank you, it was of great help and hope you don,t mind me posting it here.
autismandabamum.wordpress.com
If you put that into google, it should pop up.
Here are my (very basic) first steps to starting ABA. I've written it fairly quickly while looking after kids, so excuse me if it's got mistakes in it or if other ABA mums think I've made it too simplified, but hope it helps:
a) read the book "Let me hear your voice" - you hopefully will find it motivational and it will give you the impetus to get going
b) Find a supervisor or a consultant or a tutor - either via word-of-mouth from another autism mum, PEACH, ABA-UK Yahoo group or ABAtutorfinder.
c) Invite them round for an interview. Technically you need a consultant on top of the program (£90 an hour); a supervisor for day to day management (c. £35 an hour) and then tutor(S) - £15ish an hour. But there are so few tutors around that I would grab whatever you find, in whatever combination
d) don't worry about doing 40 hours a week or anything like that. Whatever ABA you can do is better than none, as it starts to improve the child's antisocial behaviours (which get in the way of learning) and to improve their speech/social abilities
e) Take up references from other mums on the tutors you choose, they will be honest
f) Once you have recruited, using whatever money you can scrimp, beg borrow or steal from relatives etc, sit down with tutor and set top 5 things you want worked on (eg mine were speech and aggression), Make sure the tutors know how to motivate your child (eg via a particular toy/sweet/outing). Motivation is key
g) Get going, stay around for the first few sessions to make sure you are comfortable, then gradually fade yourself off the scene
h) Use the time for a break for you, eg a coffee or a swim or whatever
i) Try not to interfere too much. The child will find it difficult at first and may object, as their life thus far has been free of any "work" or constraints. Of course they will moan when someone comes in and dictates the pace, as they have previously followed exclusively their 'own agenda'. Keep thinking - how will this behaviour look , if not tackled, when he is a strapping man of 19?
j) Have regular meetings and updates with ABA team, to refine targets. Make sure you are consistent at home with what they are doing - nothing will work if it's just for 3 hours a day, and then family undoes all the good work the other 9 hours of the day
K) make sure you and the tutors keep meticulous records of progress made, as this will form basis of your case to LA for funding or part-funding
l) Meanwhile, be applying for a statement using the diagnosis of autism