To learn a foreign language is to re-train your thinking. You must get those grandiose ideas out of your head about speaking fluently in a week or two regardless of what those online courses tell you. They are self-defeating and will lead quickly to frustration and disappointment. Dedicate yourself to the daily pursuit of achieving your goal and overcome the urge to skip a day. You know it's going to take time and consistent effort. Accept that fact and get to work. So, now that you are psyched up and are ready to work out your mind, let's start looking at what you must do to learn a foreign language properly without too much effort.
Get familiar with the grammar of your own native language. English speakers tend to be especially poor at knowing their language's grammar. Due to English's lack of genders and cases for nouns and adjectives, English speakers frequently have no idea what is even going on when they start trying to learn the basic grammatical elements of a foreign language. So, pick up a cheap grammar book at a bookstore and learn the names of the basic parts of speech and the basic components of a sentence, i.e. that the basic sentence contains a subject and a verb, and perhaps a direct object. If you are not familiar with your language's basic grammatical elements, you need to start here. Not having a basic understanding of grammar in your native language is almost certain to derail your efforts.
Dedicate 15-20 minutes, every day, 5-6 days a week to learning your new language. Set aside a time when you are particularly alert and fresh. Make this an appointment with yourself, especially if you are really serious about getting fluent.
Go and buy a basic grammar book with exercises in the target language. Get a book that simply has a number of basic exercises for learning the grammar of the language. Do these exercises for 5 minutes during your daily appointment with yourself. Because repetition is so important, don't write the answers down in the book. Take a separate notebook and put the answers in there. You can then do the exercises again later. Also, get a book that has an answer key in the back so you can correct your answers.
Get a basic traveler's language c.d. or mp3. This will help you to get a handle on the basics of pronunciation. Try to find one that also includes a workbook or brief companion. This will help you to learn how to pronounce, hear and read your target language. Don't blow the bank on this one. Go cheap. You don't need this item so much to learn the language, just to get some basic understanding of pronunciation and how to read. Reading doesn't mean that you can understand everything that you read, but simply that you can make out the words and have a reasonable idea of how they would sound when spoken. Comprehension is not the focus at this point. Dedicate 10-15 minutes of your daily appointment to this pursuit.
Although the grammar book will be likely to contain a great deal of vocabulary, find a book of vocabulary lists or flashcard program for the target language. Dedicate 10-15 minutes of your daily appointment to this. Focus on learning between 10-15 new words per day. You now have 3 different activities to do during your daily appointment. You will do 5 minutes of grammatical exercises, 5 minutes of a traveler's language instruction c.d. or mp3 that includes a brief companion to learn how to pronounce and read correctly, and 5 minutes of vocabulary learning with a basic vocabulary book or flashcards. This is a good beginning. You will make progress if you keep at it. However, there are a couple more steps in order to continue to improve your skills if you really want to become fluent.
Once you have gone through the c.d. a few times, and you feel confident enough that you can do basic pronunciation and read the words, as well as understand some basic conversation, find something to listen to in the target language. Find an internet radio station talk show or an audio book in the foreign language. Replace the time in your daily appointment for listening to the c.d. with 10-15 minutes of this listening activity. Don't worry about not understanding everything. That will come with time. Let the language wash over you.
Once you have built up a vocabulary of approximately 1,500 words, it is time to graduate from the flashcards and vocabulary lists. You will now want to go out and buy a book in your target language. Do not buy another grammar book. Buy a piece of literature. One of the best books to use is the Bible, because it is full of dialogue and is readily available in any major world language. The Little Prince is also available in many languages. Since you now know how to read words in your target language, begin reading 10-15 minutes every day. Shut the door to your room if you live with other people and read out loud and slowly to develop your pronunciation. In general, it's a good idea to have a dictionary in your target language, but it is NOT necessary for this activity. You are working at developing correct pronunciation and beginning to recognize words in context, as well as to understand complete thoughts. When you see a word that you don't understand more than once on the same page, underline it. You can go back after your appointed time period and look it up.
The next thing to do is to activate your knowledge. You want to move your knowledge from the passive into the active realm. You want to learn how to speak the language and communicate with others. Listen to music in your target language. Plan a vacation to a country where the target language is spoken. Hire a tutor to come and talk with you once or twice a week. You can even find tutors online to talk with you over the internet.
Remember, when you were a baby learning your language, you were surrounded by it all the time. No single technique will teach you a foreign language. Just like no one thing gave you the ability to speak your native language. So, combine a few different activities for a short period of time each day, on a consistent basis, and you will be surprised at how far you can go. While the struggle of learning a foreign language can be tiring and sometimes frustrating, being able to use a foreign language and converse fluently with someone in a language other than your own is an extremely rewarding experience.