Welllll playtime all depends on what you're comfortable with. I take a sheet or blanket that I don't mind using for rat stuff, spread it out on my bed and do playtime there. I set up all kinds of tunnels and hide-outs (cardboard boxes with doors cut out and lengths of dryer hose, PVC pipes or large cardboard tubes work great). Some of my rats love playing with those feather cat toys on a stick, some ignored them. They also like the jingly ball cat toys. Hiding treats for them is always great during playtime (baby carrots, peas, etc).
As for socializing, using treats is a good way to do it. I've found that it's best to allow them to trust you on their own terms rather than force them. It may take a while but some come around very quickly. They all have their own little personalities. I like to put my hand out flat with a treat in my palm and just hold my hand in the cage. Eventually they'll get comfortable enough to take it. Do this a few times a day or just sit and talk to them. Eventually you can put something like baby food in the palm of your hand (never use peanut butter as rats have no gag reflex and can easily choke on it) and they'll have to sit there and lick it off. Talk to them softly while they do this. Eventually they'll anticipate treats whenever they see you and will come to really enjoy your presence! It's not uncommon for them to "taste" or gently nibble a figertip, generally they realize that it's not food and stop after the first nibble. However if they don't stop, you can make a high pitched squeak sound, which is what their littermates would do if play became too rough.
One thing I would STRONGLY advise against is feeding treats through the cage bars or sticking fingers in the cage bars. Rats will often grab whatever is coming through pretty hard with their teeth, thinking it's food. Rat bites HURT!