Hi! I am a US citizen living with my spouse in his home country. Before I got pregnant, I made sure to familiarize myself with the CRBA requirements. Go to the US embassy/consulate website nearest to you and look into what you will need. There are different requirements for children born out of wedlock, married and between US/foreign and US/US parents. Since my spouse was not a US citizen, I had to provide 5 years worth of physical presence in the U.S. after the age of 14. I did the simplest thing on their criteria list and used my high school/college transcripts. The whole process went smoothly and we also applied for our child's passport on the same visit which I was glad to do because when you apply for a passport you have to send original documents and the idea of losing the CRBA and trying to replace it... but with them being done together, no risk. We picked up the passport and CRBA a couple weeks later. There is no crazy USCIS processing time. It's smoother and quicker.
*Also passport applications are processed faster (in my experience) when you apply at a consulate/embassy).