I have heard crontab is a good choice, but how do I write the line and where do I put it on the server?
Quick guide to setup a cron job
Create a new text file, example: mycronjobs.txt
For each daily job (00:00, 03:45), save the schedule lines in mycronjobs.txt
00 00 * * * ruby path/to/your/script.rb
45 03 * * * path/to/your/script2.sh
Send the jobs to cron (everytime you run this, cron deletes what has been stored and updates with the new information in mycronjobs.txt)
crontab mycronjobs.txt
Extra Useful Information
See current cron jobs
crontab -l
Remove all cron jobs
crontab -r