Who throws red wine on their curtains? Well whoever does is beyond help they should just give up drinking. However any minor marks chocolate or grubbly little hands can be removed in most cases with the ever important baby wipe. Every home should have a stash of these for little emergencies. Test on the inside hem first.
The best thing to do for regular maintenance is dust or vacuum at a low setting with the soft brush attachment. Never dry clean or wash, yes never. Your curtains should not be that dirty. At best hang them out on the line to refresh and blow out any cobwebs so to speak. Watch out for birds though we don't want any unnecessary "accidents". If you insist on dry cleaning be very careful where you send them. The stiffener used to create the pleats usually looses its shape and wont be the fault of the cleaners, it just happens.
Fading happens in time to the leading edge of most curtains. A good tip is to alternate left curtain to right and vice verse occasionally. A window blind will help prevent light damage and good lining will protect the rest of the fabric. If the damage is bad a contrasting border could be added to the leading edge.
Often its good to stand back and have a good look to asses why curtains are not sitting right. Usually it is because the pins are put in any old way. You know, the painter comes, curtains come down, pins go missing and they go back up any old way. Replace missing or broken pins and put them all in at the same height. Even one in the wrong place will make your curtains look crooked.
Check poles & rails.
Metal poles can be sprayed with silicone spray which is available in good hardware's. It is specially formulated not to stain fabrics. Now I didn't say spray on the fabric..... you spray the pole or rail and runners to reduce friction and get the gliders to run smoothly. if the pole or rail was put up crooked , take it down and do it properly. There is nothing worse! Did you know a lot of first arguments take place over this ?
Make sure your relationship is on solid ground before you try this or it could be curtains for you my dears.
I hope this helps.