The issues involved in dating a recently separated man can make dating such a guy more stressful than fun, as much will depend on the nature of his separation. He may have left after a long period of unhappiness and sustained efforts at making his marriage work. That is a different scenario from a man who is having a trial separation because his marriage has hit a rocky patch. In this case, you are unlikely to have a happy ending to your romance. In either case, you should exercise caution when becoming involved with a separated man and build your relationship with him slowly.
Discussing his marital status with him is not easy, as people may be normally fairly reticent at the start of a relationship, waiting to see how things develop. However, this is not a carefree romance, so you are entitled to know what exactly you are getting involved in. Avoid interrogating him or pressing for all the details of his break-up, but you do need to know how permanent he views the separation, about any children and the length of time he has been separated.
Assess your own ability to deal with any complications. If he has just separated, feelings are likely to be very raw. This will be even more acute if children are involved. He will also change the whole dynamic of the situation if he introduces a new girlfriend into the mix. This is not your fault, especially if you met him after his separation, but people are not always fair, particularly if they have been hurt.
Insist on taking the relationship slowly. Unless his marriage has been effectively over for a long time or he is cold hearted, he is likely to be deeply affected by the break-up. He may demonstrate erratic behaviour and flawed judgment immediately after the separation. Unfortunately, this sometimes involves a headlong plunge into a new relationship. Only time will tell if this is the case with him.
If he has children, take things very slowly and be prepared to deal with some initial hostility.