For a long time I had a problem that people genuinely liked me, but made no effort to reach out to me. It wasn't even that I didn't reach out to them. I would go up to them every day, but on the days where I'd be inside my head or make no effort to talk to them, I would be completely alone and nobody would come up to me.
Now, because:
a. My best friend is back at school
b. I'm apart of their classes, and thus their routine.
c. My social skills have greatly improved
The problem seems to have disappeared for the time being.
Which, obviously is no benefit to you, unless I give some suggestions. XD
1. How you present yourself is very important. If you feel shy or uncomfortable, you will make them feel uncomfortable too. Try to be, or at least come across as, happy and confident. Don't mumble. I used to mumble and talk quickly, and it's a lot easier to talk to people now that they can understand me. XD I try to smile a lot. Don't be hyper-conscious of how they're reacting to you. [Unless they're giving you strong vibes to go away.]
2. Talk about them. Find out what they are passionate about, and ask them questions about it. Show GENUINE interest! This is easy to do when you share their interests. Checking up on them later is good as well. If they mentioned their heavy work load, ask them how they're doing a few days later. Ask them in depth questions that require more than a yes or no answer. Feel comfortable with continuing the conversation. Using their name a lot helps, too.
3. Genuine compliments are great. I've found that complimenting clothes is an easy way to talk to someone, since I'm a girl XD. [I like your shoes; where did you get them?] However, if you have something deeper to comment about the person, by all means do it. The other day, one of my friends posted something on facebook about being themselves. One of my acquaintances started talking about how sometimes she was afraid to be herself. I wrote a [completely genuine] statement that everyone around her could tell how fun and hilarious she was, and admired her for it. Now, she wants to get to know me better.
Most people are insecure; do things to alleviate that insecurity.
4. If you see an opportunity to help someone, take it. Minor things like sharing food, loaning out pencils, etc, are instant ways to increase likeability.
5. Have a lot of experiences in life that you will be able to talk about. How will you appear interesting to people if you never do anything? Going out and doing things give you something to talk about!
Above all: treat everyone as if their already your friend. This makes everything a lot easier.