Find a formal English class in your area. Lessons are generally called "English as a Second Language (ESL)" or "English for Speakers of Other Languages (ESOL)" classes. Contact local colleges, high schools and community centers in your area about ESL classes.
Find out if you are eligible for free English classes in your state. Ask for information at public libraries, the Department of Education or City Hall.
Choose a level of instruction that meets your needs. Choose a beginner level class if you speak very little English. If you can hold a short conversation in English, speak with correct grammar for the majority of the time and read some English, then choose an intermediate class. If you understand most conversation, use past, present and future tenses, write essays and read books in English, choose an advanced class.
Choose a course that is suitable for your needs. If you are planning to study through English, an academically inclined course is better for your needs. If you need to prepare for a TOEFL (Test of English as a Foreign Language) choose a course that specializes in this area. Otherwise a conversational course may be better.
Check that you have the appropriate qualifications for the course if necessary. Some colleges require you to be currently enrolled or a former student of the college to take courses. Most other courses merely require you to have a suitable level of English to handle classes above beginner level.
Call the institution that offers the course to ensure the program is suitable for you. Visit the institution to register and pay for the classes if necessary. Some programs may have year-round registration.