Full EOT cleans can be difficult to get right, you may have to clean or check hundreds of different surfaces in a typical property. Ideally, you would agree with your client exactly what needs to be done from the outset and try to gauge their expectations before you give them your quote. Unfortunately a lot of clients will be vague with regards to their requirements so a lot may be left to your judgement. If a tenant has instructed you, all they really want is to get their deposits back - so they don't really care what is done - so long as the cleaning passes the checkout assessment. This is the tricky bit, whilst a checkout assessment and inventory should be impartial - in many cases the assessor (who could be the landlord/estate agent/inventory clerk), are just looking for excuses to deduct money from the tenants deposit. Some assessors will fail the cleaning for what could be extremely minor issues (say a hair in the bathroom, a tiny patch of limescale or maybe a missed fingerprint or isolated cobweb). You will probably have to go back to rectify any cleaning faults and in some cases your client many still not be happy (they may even withhold payment).
I am not trying to discourage you, but compared to carpet cleaning or other specialist cleaning services, EOTs are difficult for the reasons I've outlined. I'd say if you get more than 90% right (without complaint) first time - you're doing really well. If you've never done it before, I'd certainly advise you to work with someone who has. I know of many EOTs where the cleaner genuinely thinks they've done a great job - but the cleaning is still slated in the inventory report.