Same here.
But as for tips, I'm sure you must have heard them all before, but then again so have I, and yet I'm still a mess.
The most important one (so I've learnt/read) is to SMILE. There really is a hell of a lot of power in the smile. Obviously don't go round smiling inanely at people the whole time, but if someone talks to you/you talk to someone, smiling while you're talking/listening, at least every now and then, will surely affect them (make them judge you as nicer, friendlier, a better person maybe (the power of non-verbal cues is strong)).
But that's something to do when you're already talking to someone. What about seeming friendlier before this can occur? Hmmmm... well, once again, it's all about non-verbal cues. You have to consciously make an effort to give out the non-verbal cues that will make you appear open and friendly. What these are, books can probably tell you. I guess things like sit/stand up straight, don't sit there with your arms crossed across your chest, don't frown, don't go and sit away from people, try and put a confident and open look on your face... things like this.
BUT of course it's easier said than done, and it's hard to control these things when you're in a situation where you're anxious, plus personally I don't always like putting on a fake happy friendly act. But I suppose if you want to appear more friendly, putting out the right non-verbal cues (which as I said, I'm sure books can tell you what they are) is at least a good starting-point.
Also, an often-quoted statistic is that only 7% of communication is verbal, 38% is tone of voice etc, and 55% is non-verbal. So if you do the non-verbal and tone bit in a friendly way, then you're 93% of the way there! (yes, I am aware that that is an unrealistic inference, but it's something to think about). So maybe the fact that you don't have much to say isn't as important as it seems; the statistics above would suggest that it's not the most important thing.