The time it takes for a horse to get used to you can vary upon the horse's temperament, life experiences (if it's been abused it can take ages), - etc. Grooming is often very good. It's pleasant for the horse, and if you find they have an itchy spot they love being scratched. This can really get them to bond as grooming, scratching etc is a herd bonding behaviour horses use. You can also use food, but unless you're having lots of problems bonding with a horse (especially if they've been abused) don't over do it as you don't want them always expecting food. You can even catch the horse and take him/her to some area which has some yummy grass (if they're paddock is a bit sparse and they'd be inclined to want to graze), this can have your horse thinking of you as someone who's thinking 'for' them. (If the horse is well mannerred, and does not pose any threat to your safety) You can also just go out and spend time in the paddock that horse is in. Sitting somewhere reading a book can be good. YOur horse may come over inquisitive as to what you're doing. You can pet him/her, give them a scratch fi that's what they're into etc :). Raking up/bagging horse manure in their paddock can even help in the bonding process, he/she may come over to see what you're doing and just hang around - that's something for the bonding process as your horse get's comfortable with you and you with him/her. If you're not into reading, raking manure or doing something, just sitting in the paddock doing nothing's also fine, you don't have to hdie behind an action/activity to have your horse come by and acknowledge you.
Basically anything that has you nearby your horse can have you bonding with them.
I agree with everything shellbe said. When I got my appendix mare I had went out to look at several horses although all were nice and most a lot friendlier than she was something about her in the pasture caught my eye. I asked the owner about her he said " that one? I tell you what you want her I will let you have her cheap I am so disgusted with her I just want to get her out of here" So I'm thinking what is the deal with this horse, he went on to tell me that several people had came to look at her for a possible hunter/jumper prospect, she had also been trained on barrels at some point as well but she was not approachable, she did not want anything whatsoever to do with humans she would run off kicking and bucking like a monster was after her. I told him bring her up so I can get a better look at her and he rounded her up into a 20x20 catch pen on his 4wheeler and I went in. He kept telling me that mare is going to kill you I told him no she won't and for the next 3 hours I stayed in that pen with her. I would approach her if she started backing or walking away I walked off in the other direction totally ignoring she was there. We played this game over and over till eventually she figured I wasn't going to eat her and let me approach her, pet her and get a halter/lead on her. After that she was a doll she lead beautifully backed when asked lifted her feet everything I ask of her she did it. So I told him you got a deal and I took her home. I've had her 3 yrs now she still has her days when she doesn't want to be bothered( typical mare) but she loves being groomed and is an awesome mount. I think it takes a ton of patience which in her case no one wanted to do what I did spend 3 hours in the hot sun waiting for her to get over her fear that I was going to eat her. As far as the guy I got her from he tells me he could kick himself for letting me take her so cheaply since she has turned out to be a truly incredible horse..
Awww. That's awesome close2perfect. Some horses just need that little bit extra or a different approach. Patience and compassion can go such a long way. She sounds like a lovely mare who needed someone to give her a good go :).