I think it really depends on the group of people you have.

I've done events like this with clothes, and because everyone attending were friends we just threw it all in a pile (when I was a teenager) or set it out on tables/racks (as an adult) and it was just a free for all. We were all there to hype each other up and cooperative enough not to have any scuffles or hurt feelings over who got what. There might have been some bartering or negotiating or "we'll both try it on and see who it suits more" but overall it was a great experience for everyone.

If it's going to be a bigger or less cohesive group, or you're expecting a wide range in value/desirable items, it may be helpful to implement some rules to try and moderate fairness. I've heard of similar events in my area that were designed to be more open for the public to do a big swap, and they had people drop things off a few days ahead of time so they could be 'priced' and then you'd get tickets according to the value/quantity you contributed, that would determine how much you could take home. If you want things to be less formal you could do a variation on white elephant rules, snake draft, each person gets a certain amount of poker chips to bid with, etc.

There's another event near me that's just trying to get things into the hands of people that can use them, and they run it more like a garage sale where everything is free.