Choose types that match the data: text, numeric, bigint

The right type gives you validation and correct maths for free. The wrong one pushes checks into every piece of code that touches the column.

• Strings: use text. It performs the same as varchar(n); add a CHECK for length only when it is a real rule.
• Money: use numeric for prices and anything that must add up exactly. Never real or double precision, which round, so sums drift.
• Counters and IDs: use bigint for anything that can grow, since integer tops out around 2.1 billion.
• Everything else: use boolean, uuid, inet and jsonb instead of strings that pretend to be them.