There are tonnes of resources online with tips & tricks for photography, from really basic tutorials up to complicated post-processing techniques you can find everything under the sun. I will compile here some of the links I find most useful in case you are looking for information. I'll keep on adding my favourite ones here.
Digital Photography School - great resource of techniques, reviews and information.
Ken Rockwell's Site - also great source of tips and techniques.
Strobist - learn how to use strobes and speedlights
Stuck in Customs - HDR tutorials by Trey Ratcliff.