When you're looking for an apartment in Arcata, don't look when the weather is good. Instead, look when it's pouring. If you shop during the winter rainy season you should find some great apartments there for the taking.
Allow yourself enough time to actually meet landlords and look around your prospective apartments. Don't rush apartment viewings. Landlords often make their decision based on their sense of the individual applying to rent a suite, and if you're in a hurry to get to your next appointment, you won't have time to make much of an impression.
In California, the simple rule to remember is that life is easier if you have a car. The good news is that Arcata is small enough that there are ways to get around without one. Bicycles are a great way to travel, because there are ample bicycle lanes throughout the city, and because there is a "bike library" where you can borrow a bike if you don't have your own.
Head less than an hour north of the city and you can see the ancient Redwood forests in the Redwood National and State Parks. The Plaza is the best hangout in town, and also the site of various events throughout the year. There are also some great bars that serve local beer, including the Redwood Curtain Brewing Company.