た方がいいです　と てもいいです
 

I'm a little confused using both.

Can someone break down both of these so I can understand how it works.
Also How can i put these in negative form?

Lastly, How do you say "you must do this" ex: you must take of your shoes at the genkan

and how to say "it's okay to" ex: "it's okay to use a fork"

ありがとう
　　　　　　、幽すけ

た方がいい：it is better to do...
～ない方がいい：it is better to NOT do
靴をぬがなければなりません＝＝＞～ければ　ならない ：if you dont do it, it wont be good (so you HAVE to do it)
フォくをつかってもいい： it is ok to use the fork

hhh lol I ordered ur japanese grammar textbook yesterday, hopefully it will be delivered soon;))) I look forward to be as fluent as you are in Japanese!
貴方みたいに日本語で流暢になるのを楽しみにしてます ！！

Actually the more I read Japanese and look up for stuff in dictionaries the more those forms become confusing.
ばいい
ばだめ
ばならない
and many more started making my head spin bad LOL. It was so nice when I read my textbook...all so nicely explained. Then when they used them I start feeling dizy (;-;)

(It was just a little venting :) ).

マア、インターネットで明らかにhatsuto11さんはどのぐら い日本語ができるかを全然分からないものです。けーれ ーどっ、いままで文法の間違いや変な言い方は使ったこ とがありません。
ですから、多分もう十分で上手な日本語が使えるわけで はないでしょうか；－)
ところで、どんな本買っちゃったんですか？あれの名前 何だけ?

Just because I feel as though this needs to be pointed out:

貴方 - Why the kanji? And why not use your name?
日本語で - Should it be 日本語が? (“fluent in”の検索結果（31 件）：英辞郎 on the Web：スペースアルク)
Why みたいに with a sentence ending in ます? surely this is an imbalance?

Don't worry, my post is not just to point these things out, but also to give useful links on the grammar the OP asked about:
てもいい - Expressing "must" or "have to" | Tae Kim's Guide to Learning Japanese
方がいい - Using 「方」 and 「よる」 | Tae Kim's Guide to Learning Japanese

:)

たほうがいい suggestion
てもいい sort-of permission
なければならない／なければいけない requirement

薬を飲めばいいよ You should take your medicine.
薬を飲んでもいいよ It's OK to take your medicine.
薬を飲まなければならない You must take your medicine.

Variations on that:
薬をのんだらいいよ You should take your medicine.
薬を飲んだほうがいいよ You should take your medicine.
薬を飲まなくてもいいよ You don't have to take your medicine. [Even if you don't take your medicine, it's OK.]
薬を飲んではだめだ You must take your medicine. [Not taking your medicine is bad.]
薬を飲んじゃだめだ You gotta take your medicine. (just a contraction for the previous one)
薬を飲まなくちゃいけない You gotta take your medicine. (just a contraction for 飲まなくてはいけない)
薬を飲まないほうがいい You shouldn't take your medicine.

Note that you cannot use the ほうがいい construction to indicate past tense because it takes the past tense in order to construct the present. You can also use the present form + ほうがいい, but it has something to do with comparisons. Actually, in over seven years of speaking the language, I don't think I've ever encountered this, even when I lived in Japan. Maybe I did but just forgot.
Aw, heck, this URL explains it better than I: 38

I had always just assumed this is what this meant without ever bothering to look it up.
Glad I haven't made any bad habits lol.
Thanks for posting that link, it's a nice explanation :)

I also think reading this particular part of the quote is quite important too, since all too often I hear people being told that they can't use present tense with ほうがいい at all :rolleyes:

I have but only a couple of times.
An example was that one of my friends said something like:
映画によっては本を読む方がいい時もある。

Those may not have beeen her exact words, I can't remember too well.
But the point is it seems to me like it might be used far less.
(And going by the explanation in your link it's easy to see why :))

た方がいい is completely new to me.. the sentence above doesn't make sense to me..

Halp!

EDIT: HANG ON

Its better to read a book than watch a film if you have time?!!?

Methinks a penny about the size of king kongs testicles just dropped!

映画によっては本を読む方がいい時もある
Depending on the film sometimes reading the book is better.

In this case:
~によって - Depending on
読む方がいい - Reading is better
~時もある - Sometimes (Lit. There are also times when~)