- Remove excess matter with toilet paper
- Wash your hands thoroughly with soap after (probably the single most important thing)
- Shower once a day
- Change underwear frequently

This is the secret to having a negligible rate of death by diarrhoea disease, something the third world still hasn't figured out apparently.

In theory bidets remove more matter than toilet paper, but it's a bit irrelevant because it's not the bacteria that are there that cause a problem (there will ALWAYS be bad bacteria there regardless of what you do), it's the bacteria everywhere else.
And bidet sprayers, which you touch with your hands, tend to have more bacteria, unless they are thoroughly sanitised multiple times a day.

The one form that is strictly superior is Japanese toilets, since you typically don't touch anything.