Jumping spiders are very season-dependent - if you’re looking in the wrong season for a species, you probably won’t find anything. Juveniles can be significantly harder to find than adults, in some species.
Phidippus, for example, are mostly juveniles right now (there are a few species that mature at about this time, but they are rarer), and the juveniles are easy to find by sweeping vegatation - particularly places with tall grass, near rivers, are best. I’ve found over a hundred Phidippus in a couple of hours at times, near rivers. The adults are much harder to find because they are almost constantly on the move and usually drop into the leaf litter if they are disturbed. At least, that’s my experience with Phidippus insignarius.
Habronattus/Pellenes, are jumpers that are found on the ground - they can sometimes be really hard to find because of that. In some areas, they are littered all over the rocks / sticks on the ground, but in other areas they are harder to find. I have a few spots where they are extremely numerous (could/can find 50 in a day), but you have to have a good eye and just the right weather to be able to spot them. Plus, flies like sunbathing too and often confuse me :-)
As for the cryptic treedwellers, like Phanias monticola and Paramarpissa, these are a lot harder to find. You have to use a beat sheet or you have to get lucky and have them climb a building or something where you can easily spot them. Oak trees are great … you can also find Pelegrina on bushes and small oaks, by beating or just looking (works for me, but that might be pretty hard to do).
Lifting rocks is also great, if you’re trying to find spiders on eggs. However, this is only for people who are really really patient :-) You could lift hundreds of rocks and find nothing in a lot of places. There was one place I lucked out on and found numerous Attinella dorsata & Habronattus under rocks (even one Attinella dorsata on eggs!), but that was just one place. I’ve also found Phidippus on eggs, under rocks, but this is not very common.
And for all these jumpers, they can all be sometimes found on the sides of buildings, walls, fences, etc. Sometimes just looking in a general place where you can see them easily, if they are there, is a great way to start.
Oftentimes, it just takes general experience to be able to find these - and of course, a good knowledge of the seasons. It feels like each spider’s season is a bit different (and in certain spots, they purposely avoid each other’s seasons, amazingly, while co-existing), so you really have to look at the right times. The habitats are incredibly important too, but Buddy has already explained that pretty well. You will get a feel for the biomes of each species as you find them, and it is also quite dependent on nearby water sources (or no nearby water sources), the prey items, the range in temperatures, and even the elevation. And whether they are actually out and active is based on all kinds of weather-related stuff. Who knows, these jumpers might even be influenced by barometric pressure. It sounds trickier than it is, though. :-)
Good luck finding those salticids!! Any specific species you had in mind?