http://www.scribd.com/doc/19337272/Love-Hate-for-the-Sake-of-Allah-by-Sh...

I just finished reading this book and I have decided to share what I have learnt because I think this is quite an interesting/important topic. I hope my words are easy to understand and that you benefit from reading what follows.

Chapter One: What is Loving and Hating for the sake of Allah.

Loving for the sake ~of Allah means that you love a person because of their deen. And hating them is the opposite, aka, hating them for their lack or the “corruption” in their deen.
He (pbuh) said: "There are three characteristics whoever has them will find the
sweetness of faith: that Allah and His Messenger are more beloved to him than all
else; that he loves a person and does not love him except for Allah; and that he
would hate to revert to unbelief just as he would hate to be thrown into the
fire." (Reported by al-Bukhaaree [1/60 of al-fath] and Muslim [2/13-14 of an-
Nawawee] from the hadeeth of Anas ibn Maalik, radiyAllaahu 'anhu.)

So a muslim should love the people Allah love, prophets, righteous people, sincere followers of the prophets, the martyrs and the pious. (simplified from Book)
Ok, the confusing bit (quoting from the book) I thnk you’re going to need to read this a few times.

“and this is from the completion of his love for Allah since loving the beloved of the one that you love is from the completion of love for the one that you love”

And, logically, a muslim should hate the unbelievers (ok, don’t stop reading now, this is just the first chapter, let the author develop! Please...), hypocrites and the people of innovation and sin (this doesn’t mean calling muslim brothers “kaafir” because you “think” they are doing something of “innovation and sin” keep reading to know what the real deal is. (list summarized by me from book)