Yes, if you leave your fountain pen uncapped, it will eventually dry out and be hard to start. It depends on the pen and the ink how long that takes. To avoid the problem I have just gotten into the habit of placing the cap on while not writing. If I know I will come right back to it, I don't even necessarily screw the cap on. It may sound annoying to do so, but do it for a while and it will become a habit, and you will never notice it.
Some inks have a reputation for flowing better. PR Tanzanite is one, and the Watermans inks are even more reliable. When Inking a new pen for the first time I usually use Watermans blue-black. Some highly saturated inks will clot up faster than others. I have a pen that usually causes me no problems with drying out, but I have it filled with PR Ebony Purple right now, and it sometimes misses on the up-stroke when starting a new sentence! Just play with the various inks. And try smoothing up your nib a bit. Every little bit helps!
Scott.