- make sure you always wash your face first, and start with cleansed, toned and moisturized skin. This provides the best results. I would recommend the simple range, as they do a good variety of good quality products for skin care, and depending on which shop you go to, it's relatively cheap.
- use a primer beforehand. This helps to keep your foundation in place for a lot longer than it otherwise would. I would recommend MUA Pro Base Moisturising Primer (in sources).
- make sure you're using the right foundation for your skin type, as using the wrong one can cause problems. You may be wearing a foundation which is made for dry skin with oily skin for example, which can make it run. If that's the case, I would recommend Collection 2000 Lasting Perfection Foundation (in sources).
- use a setting powder if you're not already. This helps to set your foundation and keep it from running. I would recommend MUA Pressed Powder - Translucent (in sources).
- also use a setting spray. These are designed to keep your makeup in place all day without it wearing off or smudging. I would recommend Collection Primed & Ready Make Up Fixing Spray Matte (in sources).
Hope this helps.