I have been injecting drugs for 6 years and never once have I had to use anywhere else other than the crook of my elbow, my hands and once in my foot. If you are new to injecting there is no need to use anywhere else, you should definitely have a look at a vein map and learn about where some safer veins to use are. If im having trouble finding veins I put the palm of my hand on the crook of my arm(or wherever) and push all the skin to one side, you should see the outlines of your veins where the skin is being pulled taught. This of course will only work if your veins are not constricted.
Some tips to get your veins dilated are drink lots of water and keep hydrated, have a hot shower or stand in front of a heater, dangle your arms down below your body which will cause blood to rush into your arms causing vaso-dilation, go for a quick run/power-walk to get your heart pumping blood into your extremities, im sure theres more too just do a search. Of course using one or more of these methods together will give the best results. Personally I stand in front of the heater then dangle my arm between my legs(sitting in a chair) and I havent missed a shot in about 3-4 years, I have good veins but I honestly dont understand how experienced users manage to miss so much. If you plan to keep using then taking care of your veins should be one of your top priorities, theres nothing worse than stabbing yourself to the point of having a blunt needle and blood everywhere, its not a good look and it will prevent you from indulging in the future.