Learn the basic tenses. The present, past, present continuous, past continuous and future are the most commonly used tenses and all you really need to communicate clearly and get your point across. These tenses also use simple formulas and are generally easy to learn. More complicated tenses, such as the present perfect, present perfect continuous and past perfect, are not necessary to speak basic English.
Spend extra time on "be going to" and "get." "Be going to" frequently replaces the future tense in spoken English, particularly in the United States. Focus on different usages of "be going to" in the present, past and future tenses; for example "I am going to the doctor tomorrow" versus "I will be going to the doctor if this doesn't get better." "Get" is also a confusing and common verb in the English language, with many different meanings and usage. "Get" can mean obtain, have, purchase, understand and many other things. Learning "get" will help you communicate more in English.
Practice phrasal verbs. Phrasal verbs --- such as "go up," "get off" or "be up to" --- combine a verb with a preposition, adverb or combination of the two. Phrasal verbs are extremely common in spoken English, and taking the time to learn a few will significantly increase your basic English communication skills. You can find ESL, or English as a second language, textbooks that are specifically designed for learning phrasal verbs.
Watch TV shows and movies. Listen to native English speakers at their natural pace, using expressions, idioms, tones and nuance; this will greatly improve your comprehension and communication skills. Begin by watching movies in English with English subtitles and remove the subtitles when you feel you are ready. Training your ear to listen to English will also make it easier to understand when you are in a real-life situation.
Learn essential vocabulary for your needs. If you know you will need to be communicating in a business context, learn the most common English words in your field and related areas. If you will be traveling, focus on ordering in restaurants, asking for directions and communicating your needs at a hotel. Think about where you will be communicating and make a list of words you will need to learn.