I can only try to answer - BUT I'm an Amateur - and can not give 100% Professional advices and take NO responsibility for how they may affect You. But I will try as best as I can.
1. Is there a manufacturer that produces high quality DVD's to ensure my clients get the best.
• I only use Verbatim DVD-R as they play well (There also is Tayio Juden - never had any possibility to try these)
2. Is there a chance that my mac DVD burner might be glitchy?
• I set down burn speed in iDVD (x4) to get as few burn errors possibly
3. Does my mac DVD player/ burner need cleaned regularily?
• Mine does - I run a Cleaning DVD from time to time
4. Is there external DVD burner that I can buy that would ensure high quality DVD burning process?
• Yes but I've doubt that the result will be any better or worse - MY OPINION - I've got a ForeMac DVD burner as last resort.
5. I print DVD covers to stick onto the DVD's. Does this reduce quality or effect the playing process in anyway?
• NEVER PUT ANY LABLE OR STICKY DEVICE ON ANY DVD or CD - as they will lose in stability and result will be a MAL-Functioning DVD (or most probably not working at all - especially DVDs)
I do - use printable DVDs and use printer that accepts DVDs. They look as Pro Quality DVDs
Yours Bengt W - Sharing without ANY RESPONSIBILITY AT ALL !