It likely depends on your risk profile and age. E.g., if there is family history for breast cancer, yearly or once a couple of years mammograms. For prostate cancer, PSA levels yearly beyond a certain age and so on. The other part is just watching out for any changes/lumps and getting to a doctor before they get out of hand rather than hoping they solve themselves. The longer you wait, the worse outcomes are though for some really slow growing cancers it may be okay to leave them in because the interventions can have higher risks than the cancers themselves.

Colon cancer will be blood tests and recurring colonoscopies. Standard offering fro everyone above, I think, 50 or 55 in germany. Earlier, if there is family history. In that case, you can start as early as 10 years before the age the close relaive was diagnosed. Which means my children will have their first tests aged 16. Pretty cool, because polyps are easy to remove, ideally before they become cancerous.