Don't be afraid to use a high ISO setting. Change the iSO according to circumstances. If you are making stills with 1/300 of a second and F7.1, choose a lower ISO. If you are taking pictures with 1/10 of a second and F2,8, opt for a much higher ISO if you can.
Be practical. If you have a zoom lens, use it. Do not expect studio quality photographs (which are mostly boring anyhow). Choose interesting, vivid subject and you will be fine. Don't hesitate to discard pics that have come out badly. Have no regrets.
If you have only that 50 mm lens, you will be forced to come close to your subjects. Don't be shy! (but stay friendly and polite, of course.)
Of course, after taking each photograph, check it using the [>] button on the left of the back of your camera. Enlarge it to check sharpness. If unsharp, try and take the picture again or ajust the ISO setting if neccessary.