Second both the Vit B and warm salt water gargle.
The gargles one of the surest ways to fix mouth ulcers. The more you gargle, the quicker they'll heal.
If they are really painful, you can get a paste called Orabase from your pharmacist (pharmacist only so will have to ask at counter). You dab it on the spot and it forms a skin over the ulcer protecting it from acids, food etc and reducing pain remarkably.
Also, Medijel is a lot more effective at reducing pain than bonjela, sm33.
Drinking lots of water also helps as a dehydrated mouth can make you more prone to ulcers.
Biotene mouthwash is also good if you are getting lots of ms. It reduces bacteria in mouth as well as hydrate.