5’4" guy here. I don’t think height is a real dealbreaker much of the time. If you run into a rejection of “you’re too short” then just play the odds – move on and don’t worry about it.
(Crass punchline ahead) One time I went out with my neighbor and her sister-in-law. S-I-L is a foxy amazon, at least six foot. After spending a couple hours shooting the breeze and listening to her talk about her string of lousy boyfriends, she said, “Oh Dave, it’s too bad you aren’t six inches taller.” The barfly at the next table chimed in with, “It won’t matter when she’s on her knees.”
The real moral there is that listening attentively is a skill that cannot be over-utilized. I barely said anything other than a quip here and there, and the thought crossed her mind. I could have pursued and probably beaten the height objection with personality (It’s a complicated story why I didn’t).
If you think about it, aside from dancing, height doesn’t factor into many date activities at all. For the first couple dates, you’ll probably go to dinner, the movies or other things where you’re both sitting down.
I always like getting a second part-time job in boutique retail. It doesn’t have to be a fancy store, but maybe one of the smaller stores in the mall or something, not a Wal-Mart or Best Buy. Make a point to talk to customers, especially the ones that you find attractive and overcome your inhibitions (that’s not to say go crazy and ask everyone out, but get confident speaking to people you’d be nervous approaching otherwise). You might meet some cool people working there or they can hook you up with friends, too. I guess that applies to persons of any height, really.
Make sure you’re not slouching, short people can slouch too. Do the whole chest out shoulders back routine. If you act confident with your movements, it can become a kind of a self-fulfilling prophesy.
I totally agree with the comment about ill-fitting clothes. Shirts labeled as “fitted” or “athletic cut” tend to fit me much better than ones marked “traditional” or regular. I used to be kind of conscious about clothes sizes and delude myself into buying 32 inseam pants and larger shirts, but then one day I sucked it up, and got some 30s and smaller shirts and realized that I looked much, much better. No one sees the labels anyway. Same with t-shirts, err on the side of them being snug rather than swimming in them.
As for working out, definitely think Bruce Lee rather than mini-Hulk. If you have trouble putting any bulk on, establish a well rounded workout and really focus on abs and forearms. People in the public will see your forearms way more often than anything else, so find some exercises to build and tone them.