When using YugabyteDB, the number of shards to break a table into depends on its size and activity level. For small tables under 1 GB, colocating them with larger tables can be beneficial, while medium-sized tables (single digit GBs to 100s of GB) should aim for 8 tablets per tserver, and large tables over 250 GBs should be split into more tablets to avoid hotspots and ensure equal resource usage. The goal is to keep each tablet under a certain size threshold, and enabling auto-splitting can help with this. Additionally, indexes are sharded in the same way as tables, and there are various resources available for learning more about YugabyteDB, including blog posts, videos, and training sessions.