Before signing up:
1. Check this website:
https://www.iaco-official.org/ . They have free refereeing classes that meet all over the area starting in July. In addition to this, I believe there's a discount on registration fees, and again I believe, free registration to a clinic the first Saturday in August that is great.
2. Search for associations in your area, and email board members (depending on where in the Chicagoland area you live, I can help with this). Most, if not all, offer a mentorship program.
3. Find the youth leagues in your area, and see who the assignor for officials are. Anyone worth their salt will match you up with a group of experienced officials.
4. Attend association meetings.
5. Find a scrimmage. It's live reps.
Honestly, you could find yourself getting prelim games pretty quickly. There are guys that monitor their emails and the assignment website on Fridays and always pick up games. Getting on a crew, and getting varsity games might take some time, but in all honesty it hasn't taken people as long as it has in the past. The only guys I see not getting a consistent varsity game schedule are guys that don't put the work in.