Great advice above.
Firstly and most importantly read, read, read. Determine your pg/vg percentage 75/25, 50/50 etc then what flavors you want to use. Order your supplies like bottles, syringes, pg/vg, flavorings etc... (Read up on what supplys you'll need) then order everything. The most helpfull thing is start with making small test batches (5ml) and start with a single flavor. When ordering your flavors also order Sweetner (A must for fruits) and start with low percentages ( 1- 3%) mix, taste then add more if needed. A lot of new people to DYI think they failed after there first few batches but what they don't realize is the mix is not ready just because you've finished mixing. Some mixes may be tasteless or taste chemically or just taste bad at first because they may need to steep anywhere from a few days to a month. A hint for fruits that taste chemically besides steeping you may need to keep the cap of to let them air out or oxidize for 24 hours. This is expecially true with tobaccos, caramels, vanillas with creams added. Fruits and candies are usually vapable right away. Again mix in small batches and start with low %ages and keep a log writing everything down. It would truly suck if you found your perfect mix and could'nt recreate it. Good luck and happy vaping