Plenty of good reasons to clone. One is to sex the parent plant and see if it's male or not. Another is to preserve the genetics. And the other is to increase plant count without the differences in growth variation from differing phenos of the same strain.
I've only had luck cloning with a clone dome and potting mix. My clones were excess branches cut from the mother.
The bigger the cut. The more nutrients it will have stored. I try to make sure mine are at least as tall as a standard toilet roll.
Some plants are harder to clone than others. Mine was very finicky until I added the cloner.
I've also had great success with cloners and i currently use a clone king 36 site going on two years with 100 percent success rate, my roots tend to be much more "predator dreads" and super thick after about 5-7 days than the post above me (not that that dont look really solid!)
i dont put more than 18 cuttings in mine so there is one open space between everything but the stuff on the edges of the cloner..i use netty pots..and i cut the bases off. then ill take a nice cutting, i try to take clippings with at least three nodes, and cut with a VERY sharp blade at a 45 degree angle, and i DO NOT score the stem in any way. I then dip it in Remo roots and stick it in the foam insert that goes into the netty pot and put them in the tray like that..if there is a lot of leaf i will cut some back so there are no more than 4.
in the tub itself i have found what i feel to be a few key things to always get good success for me, some can tend to forget about this stuff and i feel its pretty important mainly the first few....
1. the water temperature. dont let cloner water get hotter than 75f...i have seen many friends not have success with cloners simply because they didnt realize the water got too hot. the pump and sprayer by their nature will ever so slightly heat up the water, so i highly suggest keeping the water as close to 70f as you can.
2. the sprayers. make sure all the sprayers work and cover the entire underside of the tray before you put anything into it. sometimes out of the box they can not function totally right.
3. water ph and additives... i keep the ph of the water between 6 and 6.5 in this stage of cutting you can go a little lower but i wouldnt go any higher if you can help it..i tend to lean SLIGHTLY toward 6.5 because i add 1 mil per gallon of water of AN voodoo juice, 1 mil of remo velokelp, and 1 mil of magcal or magnifical. then i ph to 6-6.5...if you use RO water or purified water with lower than 60ppm youll be golden...i have found the brand Primo water to be FANTASTIC for this stage of the plant because not only is it 6-10ppm (!!!) but it has a wonderful .2 or .3 upward ph flux i think due to its minerals for taste. so if you ph to like 6.2 using primo and that very very small dose of stuff, it fluxes up to about 6.5 in a few days which kind of gives the young plants a magcal boost without going overboard.
4. LEAVE THE SPRAYERS ON. leave that shit on all day and night, unless the temps get out of range..so many people say give it some "rest" time but i have had friends swear by this, and though their success rate was ok, it wasnt perfect.
5. light and humidity.. i have a tent just for propagation and i dim a veg led to about 200 watts and put it several feet above the cloner with no break in the cycle (i personally tend to veg 24/7 unless im having nute lockout), i also allow the humidity to be a bit higher in this area..in the 65-70 percent range if you can help it. lower is ok but you may need to give your plants some foliar love the first few days... i use a velokelp voodo juice spray slightly less than the ration for the tub and phd to 6.5.
FOR ME, (everyone is different of course) as i said i have had 100 percent success rate following those 5 things and i am currently on a 14 for 14 attempt record. 252-252. 8 different strains total. hope it helps!