VeggieLover

My uncle just bought me a ukulele, made by Harmony, and apparently from the sixtys. I've been practicing every spare moment I have, but I have a few questions.
The instrument itself is old, but the nylon strings are probably new, and I'm having a hell of a time keeping the thing in tune. I know it takes time to "break in" new strings, but the first string seems to go flat more often than the others. is there anything i can do to speed up the process or to fix this problem?
Also, I can't find agreeing sources as to what the standard tuning is for a Ukulele. Right now i think it's in D, which is what the little paper that came with it recomends, but I'll be taking it to an open mic next week (just to jam around and show it off mostly lol) and i want to be able to play with some ppl, what is the key most likely to fit with other instruments?
I know about 4 chords (don't know which ones really, especially with the discrepancy above) and I've been playing around with my own song, nothing special but fun for me to play. Does anyone know of a site that would help me learn a bit faster?

Thanks, I'm kind of obsessed with my little instrument, and I'd like to talk with anyone else who plays

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