I am a fan of manual myself but since this is brought up do you have multiple registers were your domains are hosted or do you keep them all under 1 roof?
I am moving all my domains under 2 registers one I have my active sites under the other inactive sites with my hosting company. I have tend to visit the register more often and stay informed of when my domains are expiring or possible terms of service changes that can happen without notice.
Sometimes my credit cards are kinda full so it best me do it myself. :)
This as well lets me decide if keeping the domain name is worth it now and or let it drop. I have let 5-6 go in the last month.
When managing domains, it's also a good idea to make sure you know the renewal price if you are setup for autorenew. I had a novelty extension that was transferred into my registrar for $9.99 and had a $30 autorenew charge when it was time to renew the domain.
On various forums I have seen registrars being abused for not providing it auto renewal and being accused of theft when debiting credit cards for contracted auto renewal. The moral is to know what you are signing up for and what your responsibilities are up front.
And make sure that you white list the registrar in your email but keep your own diary of renewal dates. I have seen people loose their domains because the renewal notice was spam trapped.