Service own group & user ids

Hello everyone;

I have posted a link some weeks ago for OpenStreetMap OVERPASS installation guide for slackware. The dispatcher server cannot run as root, so I created its own user and group with an arbitrary id's; just like was done in the postgreSQL slackbuild script. The question is what are the rules to choose those id's? What standard(s) do I need to conform to? Now I know those ids should not be high numbers like I did.

Thanks in advance
Wael Hammoudeh