Fixing Invalid Characters in RSS Feeds.. ?

I wrote a custom blog/CMS script that I use to generate RSS feeds. Every so often, in the process of cutting and pasting from other sites I will inadvertently enter a bad character that RSS doesn't like which causes the whole feed to break. (For example, versions of quotation marks or long dashes). My solution now is to check the feed at feedvalidator.org and then edit any offending characters by hand. Does anyone know an easier way to do this? In truth, I'm not sure I know what kind of characters are valid and which are not and why. Is there an easy way to validate and correct any incoming text? Thanks, - schnippy