What's the best way to auto populate a field dependent on another field?

[nmcl]

I'd like to implement something where by if a certain priority is set (e.g. P1) that the 'Major Incident' template is inserted.

So that the description and short description fields are populated with template text.

What's the best way to go about implementing this?

[jmrece]

Hi,

As per my development experience "Data lookup rules and Assignment lookup rules" are best way to auto populate few fields based on some fields which we selected in form.

If you need any help, let me know   at jmrece@gmail.com