Start off by using normal dish washing liquid and rub it into the stain. Then rinse the stained area in hot water and repeat the process, if the stain isn't gone.
Some stains will require stain remover and some more dish washing liquid or liquid wash detergent. For colored garments, make sure to use color safe, non-chlorine/bleach-free stain remover. Work the stain remover into the stain and let it sit for around 10 minutes. Don't rinse, but add dish washing liquid or liquid wash detergent into the stain remover on the stain. Let it sit for around 10 minutes.
If the garment is washable, wash it according to the care label instructions. If the stain isn't gone when the garment comes out from the washing machine, repeat step 2. Don't steam or iron the garment if the stain hasn't been removed completely, this will only set the stain and make the continued removal of it harder.