Wash twice - once when you have just brought it and secondly when you are going to sell it.
Change the oil and filter twice a year or 6k miles.
Service it the same times as you change the oil. Only use oem oil filters.
Check often the bits that wear - brakes, bearings, tyres, chain & sprockets. How frequently is down to you so pick somewhere on the OCD to lazy spectrum and use that as a guide.
Don't grease anywhere it is dangerous - tyres and brakes do NOT need greasing. Nor do nylon coated cables as it makes them swell.
See the bike as something you should enjoy but are probably not going to keep forever.
Check/change the antifreeze and brake fluid every 2 years. Check the battery as frequently as you can be bothered to but don't be surprised if it is not checked and the bike fails to start.
Try and buy a bike off someone who is anal. You get more fun out of it when you abuse it.
Try to wear tyres out on both edges, not just the centre. They are expensive so get your money's worth out of them.
Spend any saved maintenance money on fuel. It is for riding not an object d'art - unless it is a Ducati 916.
Loads more wisdom's from the "house of the dirty dt" but I am at work so I need to go and save a few people before rushing off to get some tread on my quite worn tyres this pm.