OK, well I don't know anything about
BAs (not read their latest codex) but in general:
1. Keep together. Don't spread out too much as your force is a small one and needs to stay compact. If you spread out you do not have the numbers to take things on with any kind of concentrated attack and will be vulnerable in return.
2. Concentrate on your targets. That means try and have multiple units supporting each other when attacking. Make sure you cripple or wipe out enemy units. Don't spread your fire/assaults so that you are doing minor damage to many units.
3. Remember to protect your scoring units - don't throw them away. Keep them safe.