People sometimes think of mingling like it's a mechanical process. I know some advice on how to do it can unintentionally give the impression that you need to approach it that way. In practice it's not really a matter of, "I will spend the party making the rounds and speaking to people. I must talk to 75% of the people there. I will make each interaction six minutes long. I will acquire the following information from each person..."
In my experience at parties it's best to go with the flow, talk to the people who seem fun and interesting to you, and see where the night takes you. If you want to try, go for it, but don't feel you have to talk to every last guest. There's no party rule that says if you're a bad person for not doing so. A lot of people don't. You've got to make decisions, and often you'll decide you'll have a better time if you keep chatting to the really funny people you've met in the kitchen, as opposed to breaking away to introduce yourself to that new insular looking couple that just showed up.
For whatever reason, two metaphors come to mind when I think about mingling at parties. The first is to see a party like a fairground. At any party there are all these sub groups, conversations, and activities going on. One group is talking in the back yard, another is on the front porch, some people are playing video games downstairs, four guys are playing flip cup in the garage, some women are telling travel stories in the living room, some roommates are talking in the kitchen, three people are doing shots in there as well, and so on. At the party everyone is moving around throughout the evening and visiting the various 'fairground booths'. Some people will stick to one for a long time. Others will check out a bunch quickly, then go back and forth between two of them. As the night goes on new things to check out will pop up. There's no 'right' way to see all the attractions, you just have to wonder around and head towards whatever looks fun.
The second metaphor, which gets at the same idea, is that I picture people at a party as a bunch of ping pong balls floating in a tub of water. The balls will all drift around on the water's surface. For a time a few balls may cluster together, but then they'll break up and maybe temporarily group with a few others (I have no idea if this is actually how a bunch of ping pong balls would behave in water, but let's go with it). Basically, the movement of people from group to group is spontaneous and chaotic. Someone may to be talking to one group, then see their friend doing something fun and leave to watch what they're doing. Then they need to use the bathroom and run into someone else on their way back, and end up going outside with them. Again, go to a party intending to just drift along like this, don't feel you must start at the front door and systematically work your way around the room or anything.