As far as restaurants, yes, you only tip at table service, and it's based on the quality of service. But, if the food really stinks, say something about it and your server should try and make it right. 18% is fairly standard for good service these days. WDW prints suggested amounts at the bottom of receipts, and a few off-site restaurants do too, but not all. Also, you tip on the amount of the bill before tax and before any discounts.
For hotel maid service, it's a matter of personal choice. A lot of people prefer to leave a daily tip of $1 per person in the room, but it's nowhere near as universal as tipping waitstaff.
Other common people to tip:
Bellhops, porters, skycaps, etc who handles your luggage - $1-2 per bag is common
Valets at parking - $2-5ish, and you usually give the tip when you get your car back, not when you drop it off
Taxi drivers (this is different if you use services like Uber/Lyft) - A similar percentage of the fare that you'd tip a waiter, plus a similar tip as a bellhop or porter if the driver handles your luggage.