You need to have a good textbook of some kind. I will assume you have already found something suitable. If not, try searching for "Hindi grammar" on Amazon; this will bring up a number of titles. Check out the reviews to see which one(s) look best. You may find it helpful to have two or three textbooks, as sometimes one covers a particular area better than another. A reference grammar is useful for advanced study, and sometimes for clarifying points that textbooks leave unclear (some textbooks are better than others).
You should get at least one book that is bundled with CD's in which exercises are spoken. It will also be helpful if the recording gives you some drills to learn how to distinguish certain sounds which English speakers find hard to distinguish. In Hindi this might include nasalized vs. non-nasalized vowels, or some of the retroflex consonants.
Work through the book of your choice. You may then find it helpful to go through the same book again to consolidate your knowledge, or you may want to work through a different textbook. This will not only help consolidate your knowledge, but give you a different approach to some points, which may prove useful.
It is also important to listen to Hindi as much as possible. Nowadays you can find audio files of virtually any language on the internet. You may find radio and TV programs, recorded conversations, prose texts, poetry or music. This listening will help you learn to process the spoken language in a natural form, including fast speech, colloquial speech, speech with hesitations and errors... all the sorts of things you normally find in everyday conversation.
Since you have no one around you who speaks Hindi, you can practice speaking it yourself, perhaps even recording yourself. Or if you have a friend, wife or girlfriend who is interested, you can study together and practice conversing together. This is not as ideal as having a native speaker to talk with, but it is definitely better than no conversation partner.
As for memorization, it is a good idea to memorize a certain amount of vocabulary and paradigms. I find it helpful to use index cards. I write the foreign word on one side of the card in its usual alphabet, and the English on the other. On the foreign side, I include, in a lower corner, important inflected forms, if any. For nouns, this includes irregular plurals, possessed forms or case-inflected forms. For verbs, this may include a present stem and a past stem, possible a participle or an infinitive. Find out what the "principal parts" of verbs are and learn them for each verb from the very beginning of your study. This will save you from having to learn a large number of such forms in the lesson where they are introduced. See my blog entry (http://syriacspanish.blogspot.com/2008/09/learning-arabic.html) for a concise discussion of this issue for Arabic. Actually, if you look around my blog entries, you will find quite a bit of information about language learning from my own experience over more than 30 years.
In addition to learning individual vocabulary items with their respective inflected forms, you need to learn paradigms, that is, verb conjugations and noun declensions (to the extent that Hindi has either). I find it best to use a model verb, which you will find in the first lesson that introduces the full conjugation of a particular tense. If Hindi has multiple conjugations, like Spanish or Latin, make a separate card for each model verb. Put down all the inflected forms as they are shown in the book. I find it best to learn whole words, not just sets of endings. Some highly irregular verbs (commonly, ones meaning "to be," "to go," etc.) will have to be learned separately. Write the inflection on one side of the card, and on the back write something like "present tense of 'go' ".
Write a batch of cards for each lesson. Practice going through them first looking at the Hindi and then checking the English to see if you have it down properly. Then go through them the other way, looking at the English and seeing if you can produce the Hindi. Say the Hindi words out loud as you go each way. This will activate another channel of the brain in the learning process. You may even find it helpful to walk around while memorizing. This gets the whole body involved, even if indirectly.
My correspondent and the group of friends with whom he was studying wondered why I had suggested walking while memorizing. Here is my answer:
Walking is strictly optional. However, if you move around while memorizing vocabulary paradigms, it seems to have two effects1. It keeps you from dozing off because of the tedium of memorization.2. It involves more of your whole self in the learning process. The effect is not direct, but indirect. Consider the analogy of smell. A woman might wear a certain kind of perfume on her first date with a man. After that, every time the man smells that perfume, he will think of his first date with that woman. Or there might have been a distinctive smell of some food cooking at the restaurant, and later on, that smell will remind the couple of that experience. Similarly, if you take a firm step each time you recite a form in a paradigm (Amo, Amas, Amat, amAmus, amAtis, Amant...), your subconscious registers the emphatic physical action along with the stress of the word. It provides a subtle means of reinforcement.If the members of your group want, they can try it and see how they like it. Some may find it helpful, some may not. To each his own. I have been helped by such things, and so have other people I know; that is why I mentioned it.
For learning word order, you may find it helpful to memorize model sentences. Many textbooks have dialogues that they recommend you memorize. Definitely make the effort to do this. It will repay you many times over. It will help you get accustomed to normal modes of expressing yourself in Hindi. You will have to get used to putting the verb at the end of the sentence, to putting the equivalent of English prepositions at the end of words, etc. (bits of Hindi grammar I have just gleaned from the internet).
And of course, if and when you do come across speakers of Hindi, try out what you are learning. Most of them will be quite pleased that you are making the effort and will want to help you learn more.