Oh, and if you are inexperienced, it is common to being pushing too big a gear at too slow a cadence. I don't know if that's an issue for you, but in general keep a nice smooth, relatively fast cadence.
That is the first thing i learned from this forum several months ago, and it has served me very, very well. It's turned into one of my 'riding mantras', when things start getting tough....'spin more, mash less'...