The first step is to actually ask in the forum and read the reputation threads available for all to consult. This is curated one-tomany content that will serve you well if you need to check the reputation. Reading the ToS is usually quite boring, but I am afraid that if you are going to request certain level of service or withdrawals you have to assume that there may be limits, so check first to avoid disappointment.
The terms and conditions for the casinos are not very lengthy and it may take 10 to 15 minutes to read them in detail. It is important that gamblers spend this time in the terms, and not face surprises later. Gamblers usually do not read the terms initially and when they experience any abnormal treatment, they do not know that it was mentioned already in the terms of service.
By the way, any gambler who is active on this forum will never have to face this issue of knowing whether he is gambling on a reliable casino or a suspicious one. Just read the last few pages of all the ANN threads and you will know what's going on with each gambling site.