Just though I'd say hi and welcome to the forum and the world of running!! i find running for charities is a huge motivator...if youve convinced people to sponser you then your kind of committed to doing well!! Only works a once or twice a year though..people get fed up if you hound them for donations every time you race!!
My cousin runs for Charities as his mother (my aunt) died of cancer.
At the same time my aunt died my mother was becoming ill.
2 years later sadly my mum passed away with cancer too.
I do not aim to run for charity this year.
I aim to run because I like it and want to build up my running time so that I am comfortable with it. But who knows I may do better this year than I thought I may be able to. Time will tell.
Any advice for a beginner will always be welcomed.
Best advice is to enjoy it and don't take on too much too soon, if you up your mileage the general rule of thumb is 10% each week, this will help to avoid injury.
Most importantly if you have not done so already is get yourself fitted out with a proper pair of running shoes find a local running shop and have a gait anaylsis done and this way you get the right running shoes, this may sound over the top but it will be the best running investment you make.
Joining a runing club is probably the best thing I've done since starting to run (that and having gait analysis). It's a great motivator and will help you improve no-end... most clubs cater for all abilities too :d