I hardly ever use up my 30 daily votes. The one thing i make sure is that i upvote well asked questions (not just the good answers) in SoPW. Writing a well-designed request for assistance takes time and effort(*), and upvoting those encourages the requester to use just as much effort on the next questions.

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(*) Writing full sentences with a beginning, middle and end. Using puncuation and paragraphs. Including a SSCCE. Bonus points for stating wich Perl version and Operating System is used, as this makes it much easier to check for well known bugs.