Besides having high trade tech:
- don't send a lot of traders into CoT's controlled by Spain or Mughals. They tend to ban you. Keep 3-5 traders there otherwise you'll run at a high risk, especially when they don't like you.
- early in the game it's very easy to successfully send your traders since noone else is around.
- don't trade maps or loose naval battles later in the games when you have a hidden profitable CoT in ROTW.
- sum the # of traders in a CoT. Your chances not to compete someone out is higher if the sum is below 20
- competition means lower relations. Lower relations means the risk of being banned.
Otherwise you'll have to precise your question.