wet the shirt and put some salt on the area where the stain came ... i hope you washed the shirt immediately after the stain? if not , then the stains can become rugged ...
There are so many stain removers in the market, you should always keep one at home ...
cold water can help and also try a good detergent such as Shout, Tide, or Oxy Clean. Check your local supermarket for stain sprays and good laundry detergents.
Or take it to the dry cleaners.
I've read the cold water is good for ketchup stains. Try that. Soak it in cold water for several minutes. Don't use hot water...I've read that it can make the stain more permanent.
a mixture of viniger and baking soda might work with some hot wtr while washin it. once i had a nasty stain on my fav top n wasn sure of its origins so tried dt wid some good stain remover n detergent n it worked.... using only satian remover dint work for me.....