Best practice for migrating from Legacy system to Dynamics

Hello,

Does anyone have tips / can refer me to  a good post on best practice when moving from a Legacy system to Dynamics AX/ 365?

I'm looking to read more about what types of rules to follow when bringing in vendors etc. with old number series to new.

What are pros and cons of establishing the same number series / intelligent number series in the new system?  what do we gain if we make the number series automatic in new system?

This is just an example. What other things should be consider as best practice when migrating into Dynamics world?

Thanks!

Loku