The 3000 most common words in italian make 95% of normal speech. This rule is probably also valid for the language you want to learn. Once you master these words, you have a vocabulary that is sufficient for most general conversations. If you also mastered all the important grammatical structures, then you can begin advanced learning. How should you work now ?

Read, listen to radio, watch TV. There are thousands of resources on the internet, hundreds of magazines and newspapers where you can see your language "live" and confront your skills with a permanent test.

Find people you speak your language, be it trough travel, ads, local community centers, or whatever other mean. Speak with them, listen to what they say.

You should NOT be happy with being understood. It's easy to be understood and you will not command respect from the people you talk to if you speak to them in what will look to them like baby talk. Instead, you should always try to make your pronunciation perfect, including intonations (it's very difficult in english, very irregular). When you make a mistake, insist to be corrected and write the correct phrase.

How not to forget the language you learned :

You must organise your life so that chances to practice your language come by themselves : travels, newspapers, setting your TV on foreign channels as default, marrying a foreign wife, etc...