When I was a kid, the $1 egg rolls from the Chinese restaurant that used to be on the corner of 54th and 9th in Manhattan was my after-music-school snack. The ones there were fat and greasy, using the standard Chinese-American style wrapper: thick, with a blistered, bubbly surface. I'd empty a pack of sweet duck sauce over the top before downing it—they were crisp, with a steaming filling of cabbage, carrot, mushroom, and salty char siu pork. When well-made, they're a delicious study in contrasting textures and flavors.
Though the term "egg roll" and "spring roll" are occasionally used interchangeably, at least in the Chinese-American lexicon, the difference comes down to skin thickness and size. Egg rolls use thicker wrappers that blister with bubbles, and are generally stuffed to the brim. Spring rolls feature a paper-thin wrapper that's less doughy, and are minimal when it comes to filling, maintaining a slender, hot-dog-sized shape.
I like mine somewhere in the middle. When I make them, they're closer to egg rolls in size, but use the thinner, crisper spring roll wrappers.
You can make the wrappers yourself it you're really hardcore, but frozen ones work great, and are readily available in the freezer section of Chinese groceries (check near the frozen dumplings).
You can fill them with anything you like—greens, vegetables, noodles, or minced meat or shrimp all work—but I like the cabbage/carrot/mushroom/char siu combo of my youth. Buying the char siu pre-roasted from a Chinese barbecue makes the whole thing come together really quickly.
Rolling egg rolls or spring rolls is just like any flat-starch-around-moist filling roll: you have to keep things nice and tight. Loosely rolled egg rolls will fall apart as they fry, or at the very least, leave you with greasy pockets in the finished product. Not a good thing.