Good schematic checklist
Functionality:


Check symbol pinouts, especially for new symbols and parts with multiple packages.
Review vendors' latest data sheets and errata to see if anything has changed since you downloaded it.
Have the vendor's FAE review the part of the schematic that uses their part(s)
Label all power nets consistently.  Makes it easier to find them during the PCB design.
Check for on- and off-page connections, using the tool's DRC.
Check for same net on different pages without on/off page, using DRC.
Avoid strange symbols (e.g. #) that other tools may not handle well.
All upper case.
Show revisions.  Show when drawn, whom by.
Think about EMI/EMC/FCC/UL/CE, etc.


Ease of use:


No 4-way ties.
Label all important nets, e.g. clocks, power even if only going between 2 chips.  Makes checking if the clock's serial termination resistor is near the clock driver.  Also good for high-current signals that aren't the main power rails, e.g. around the FET or inductor in a DC/DC switcher.
Table of contents on an early page; block diagram on an early page.
Show power and ground on schematic symbols.
Show unused gates/resistors from multi-gate/resistor packages.
Show active low pins on symbol; show active low nets consistently.
No extra connection dots where there isn't a connection.
Not larger than B-sized (11x17) or metric equivalent.
Bus common signals.
Connect by name on-page if it makes it more readable.  Similarly don't wire power/ground all over the page, use multiple power/ground symbols.
Inputs on the left, outputs on the right.
Everything on a grid.