There was a thread about minimising during the moving process about a month ago that has some ideas.
I liked the Marie Kondo book for helping pare down - if you want an idea of what's in the book, her method is summarised pretty well on Buzzfeed (scroll down until you pass the stuff about breaking up). If possible, work through in the order she recommends. If not, start with the things you won't use for a while (off-season clothes etc) so you can decide what to move and what to get rid of.
Consider, when discarding, the life you actually lead - not the life you want. If you never entertain more than 2 people at a time, is it worth having a dinner set with 8 place settings? If you enjoy making art but never use the sculpting materials that take up a huge box in your studio space, wouldn't it be better to keep the markers and pencils that you do use and enjoy? If you're happy to have someone else develop your photographs, is it important that you have your own darkroom set-up? I knit, for example, and recently discarded most of my needles and tools - I kept only the ones I use regularly and enjoy using (e.g. no straight needles, because I'm really not a fan of knitting on straights). I went through my yarn with an eye for what kinds of projects I like knitting and discarded a lot of stuff that had been sitting around for a long time without inspiring me.
Another thing I've done is to limit my memorabilia to a single container. Anything that doesn't fit has to go. I'm still working through it all but I am definitely finding that helpful for deciding what is worth keeping and what isn't. It's also helpful to think about why I'm holding on to it all - mine is for future family to see, so it's not worth keeping every single photograph I ever took, or every report card I ever received. I'm trying to keep only things that are representative of particular times in my life, or have a longer connection with our family history (passed down for several generations). It's important not to keep things just because you've owned them for a long time.
Hope some of this helps! Good luck with the process and with the move.