An important etiquette rule is never to rest your chopsticks across your bowl, as it signals that you are finished eating, which looks rude to the chef if there is food remaining.
While you can use a spoon or slurp up the broth right from the bowl, using your chopsticks to eat solid items such as vegetables, meat, beansprouts, or dumplings is customary.
As well as reassuring your hosts that your meal is going down well, slurping is thought to enhance the flavor of dishes and has the bonus of cooling down your noodles.
If you're eating at a ramen-ya, the idea is to get in, enjoy your ramen, and get out, as most head to ramen shops for a fast, convenient, and tasty lunch where speed is key.