Grief is non-accepting Dukkha. It's usually a reaction to loss, loss of something, loss of what we considered to be ours or mine, and so it is non-accepting of Dukkha and a non-accepting of the reality of life.
What kind of meditation can I use to avoid grief? It really depends on what type of grief it is, because there are different types of meditations to deal with different types of losses. So I can't really say which type of meditation to use for which type of grief, it would take too long. But, for instance, if you've lost a loved one, usually what we recommended is the D/D method to gain insight into understanding the universality of death, together with the reflection on the beneficial qualities of the person who has died, wishing them well wherever they are. In this way, we can start to re-focus our attention towards the person who has died and putting our energy towards doing something beneficial for that person, rather than thinking about ourselves and what we have lost. However grief can arise from various types of losses, so different types of meditations are recommended depending on which type of grief is arising. If there is a particular kind of grief that you would like to neutralize, then please ask in an interview.