It really depends on what/where I'm shooting. I have a back pack that can carry/store most of my kit so it's to heavy to bring everywhere so it normally gets left behind with what ever gear I don't think I'll need at the most convenient location(like in the car).
If I'm going to walking around and shooting for a long time(like at an event or hiking for wildlife/landscapes) I'll use a single/dual sling and a belt system if I need to bring other things like lenses/TCs/filter packs/speedlites.
If it's something that doesn't require a lot of walking/time(like stopping by a vista point for a landscape or BIF). I'll just grab camera/lens and and hand carry(sling over my shoulder if a tripod/monopod will be used. Filter pack and TCs if needed will either just be hand carried or put on standard belt(the used for my pants).
Underwater I use a Pelican case which keeps the gear safe and dry while easy to wheel around.
I'd like to pick up a couple of sling bags, one small and a bigger one(like the Tamrac Evolution series) for those times I'll be out for long time and will likely want to take pictures but won't be that often. I think a vest might come in handy at times so I might pick one those up as well since they're cheap even though I haven't had a real need for one.