Left Back

Played there myself a while ago and had a mare, if you're right footed try not to drift infield, support your winger and try not to get done in behind (so to speak)

Also make sure you look along the backline so that you don't drop too deep compared to the rest of the defence. You don't want to be the one playing the opposition forwards onside.

Similar thing happened to me. I play left mid or centre mid but when our lb got injured I got asked to take one for the team and play there for a game (greeted by a lot of moaning on my part, mind).

Anyway, turns out it's a fun position to play in. As above, make sure you look along your back line frequently, remember to rush out once corners/crosses are cleared. Positional awareness is (in my opinion) the hardest part about it. You often find yourself squeezing infield and taking the striker off of a cb's hands for a while.

I don't know your attributes but with me, I'm the fastest on the team and technically decent, so tricky, pacey wingers weren't a problem for me.

I do concede that I struggled with some of the physicality of the position as I'm just 5'11 and despite religiously hitting the gym I'm quite skinny.

Best advice I could give is be the most confident player on the pitch. Scream for the ball from kick off, give an option for your cb/keeper when playing it around at the back. Offload up the line to your winger or an open cm and sprint for the return.

You often find yourself in a lot of space when venturing forward as most teams at this level (semi pro in my instance) don't expect the over lapping etc.

I'm left footed so crossing was natural from that side but I'm sure with the space available, once exploited, you'll have more than enough time to cut back on to your right.

Agree that positional awareness is the key. Depending on how good your fitness levels are you want to get up the field and support your winger as often as possible.
Hopefully your centre backs will be very vocal and help you out, but just bare in mind that you should never be any deeper than them (unless you've just been skinned and have to sprint back!) because they'll be the ones bossing the offside line.
When I play full back i also try and come short (whilst staying wide) to give the goalkeeper an option to pass to, either from goal kicks or when he's had it passed back to him. Unless their winger has a very good engine on him he's unlikely to track you back there (not that all wingers are lazy, but the position demands that they sprint a lot, so they'll usually conserve their energy for things like that).

Best of luck