What features do you look for when choosing a residential proxy provider?

I am looking for a good residential proxy provider and would like to hear from people with experience. What features do you think are the most important when choosing one? Do you focus more on speed, realiability, IP quality, pricing or customer supports? I'd will appreciate any advice on what to look for and what to avoid.

For me the main things are IP quality, pool diversity and how well the proxies actually work on my target sites. A huge advertised pool means nothing if the same subnets keep repeating. I also check sticky session length, country/city/ASN targeting, real speed under load, traffic pricing and whether support can actually replace or investigate bad ranges.

Best advice: always buy the smallest package first and test it on your exact use case.