Well, a language generally is used in four forms: Reading it, writing it, listening to it, and of course, speaking it. A person can't be said to be fluent in any language until he or she has good control of all of these areas. Generally, a person will be more proficient in some areas than others, so it's best to target weakspots.
Some suggestions to improve in all four areas might include:
- A native speaker is the best thing you could do. It will help you face a realtime conversation, and help with pronounciation (or sounding natural.) If you can't find anyone in your community, you might try looking online, as there are a lot of people that would be more than happy to Skype.
- LISTENING: Good listening skills are important to make sure that you can recieve verbal instructions, but the level of necessity depends on the language (e.g. It might be harder to listen to Chinese than Spanish because it uses many pitch-accents.)
- Listen to music or watch movies in Spanish. If you can't understand what's being said, replay it, and try to focus on which sounds are hardest. (Note: use clear recordings, as noise & static will make the process much harder than it needs to be.)
- An online listening comprehension test is also a great idea.
- WRITING: While Spanish is written rather phonetically, accents can be a bit hard to remember, and even natives can make mistakes with them from time to time.
- Online language social networking sites like Lang-8 and italki are great since everything you write can be checked by other natives. Using these sites to keep an online journal will also help you see & track your progress over time.
- Use a spellchecker, but don't be LAZY! ;) If you see that you've spelled a word wrong, try to practice it.
- READING: In Spanish, reading is probably the easiest of the four areas, and generally the one mastered first.
- Read Spanish novels, newspapers, blogs and websites.
- Keep a good Spanish dictionary with you or on your PC & phone.
Lastly, the most general principles of a language that are not tied to any one of the four specific areas of use discussed above are: vocabulary and grammar. These are learned fairly easily, and you'll pick them up as you try focusing on use of the language.
In short, just try to use the language in every way possible.
Hope this helps :)