From past experience, here are a few interval durations that work well:
 

There are two options available: Auto exposure or manual exposure. The duration of the timelapse and the nature of the subject will affect this decicion. The key is to avoid unwanted flicker at all costs. The issue with selecting auto-exposure is that momentary changes in lighting and reflections in the lens can influence the meter in the camera. This creates flicker in the final movie as the camera suddenly tries to adjust to these changes.

If you’re shooting a time-lapse in even lighting or for short durations, set the exposure to manual and you won’t have to worry about this.

If you want to make a 24-hour cityscape shot, you’ll have no choice but to use auto exposure, as you can’t expect the nighttime shots to require the same exposure as daytime shots. Shots in which the light changes dramatically will also require auto exposure, such as in-car time-lapses. Note that you can set the camera to aperture priority so you can preserve depth-of-field if necessary (just make sure that you don’t hit either end of the aperture scale during your time-lapse).

You can also choose to manually set the exposure even under changing light, such as a sunset that fades to black.

Also, set the ISO at its lowest setting - remember that you want slow shutter speed. Low ISOs also make for less noisy images.

It you choose to use auto-exposure settings, make sure the metering is set to average out the viewer as much as possible, because you don’t want the exposure to flicker as it tries to adjust to whatever's in the center of the viewer. Also, make sure to block the eyepiece with a piece of tape to prevent sunlight from leaking into it and throwing off the meter.

Make sure that the white balance is set to a manual value (i.e. Daylight or tungsten) because Auto WB tends to give unpredictable results from shot to shot.

Sometimes what makes the motion in time-lapses appear so jerky is the fact that there’s no motion blur between shots. If you were to freeze some regular video footage, a moving subject is usually captured for half the length of the frame rate (which would be about 1/12 of a second for motion picture film). You can see faint but perceptible motion trails from frame-to-frame. Each frame blends into the neighboring ones.

While playing back time-lapse movies, these motion trails are not present, making the motion appear very sudden and jerky. If we wanted to create these motion trails, we’d have to make the shutter speed half the length of the interval of the time-lapse. For example, in a 10-second interval time-lapse, you’d have to expose the frame for 5 full seconds. Even with the aperture closed at its maximum, and the ISO rating at its minimum, you wouldn't even come close to that long an exposure. Neutral Density (ND) filters can greatly help achieve such slow speeds especially in broad daylight. Try it, you’ll see the difference.

You don’t need the biggest image size and quality to shoot time-lapses. Your main concerns will be storage size on the camera and media handling in post-production. If you think that shooting 8 megapixel images will help the quality of you time-lapse, you’re wasting precious storage space. Just to give you an idea, here are a few approximate megapixel ratings for common movie formats:

Standard Definition	0.3 MP	720 x 540 pixels
High Definition (720P)	1MP	1280 x 720 pixels
High Definition (1080P)	2MP	1920 x 1080 pixels

  
Considering that you’re not going to see any extra detail in the timelapse, there’s no point in setting the resolution any higher than your final output size. The only exception to this is if you’re planning to create Pan&Scan animations of your time-lapse in post-production. For web broadcast, anything over 640 x 480 pixels is going to require loads of bandwidth.

Since on the vast majority of time-lapses the camera won't be moving, there is no point in enabling autofocus. Focus hunting will be very distracting in the final result. Also, servo AF will gobble up battery life as the camera always hunts for proper focus.

When setting up a shoot, always plan for the worse, especially if you plan on leaving the camera unattended. I accidentally destroyed one of my cameras because the wind picked up and toppled the flimsy tripod it was on. Here are a few considerations you need to plan for:

The weather - even on a sunny day, plan for bad weather. Put a ziploc bag on top of your camera with a corner cut off that fits snugly around the UV filter (don't leave the lens bare), that way if it rains or if dew condensates, it won't harm the camera. Make sure the tripod is sturdy, and weigh it down if necessary.

Onlookers - They will mess up a few frames if the wander near the camera while it's shooting, but even worse they might screw up the entire time-lapse if they touch something. Make sure the area where you're shooting is off-limits (use yellow caution ribbon if necessary). Make people aware that a time-lapse is in progress. If shooting in a public place, alert security personnel that you'll be there (they might even give you access to interesting vantage points, like building rooftops). Make sure to put a sign on your camera stating that this is a "Time-Lapse - do not touch" and also include a number where you can be reached. Security guards are not too keen on letting someone shoot on their properties and will not hesitate to remove all your gear if they feel it might be a threat. Also, when shooting indoors, tape the light switches so someone doesn't inadvertently flick one on.

Camera
Media Card
Timer (a.k.a. controller or intervalometer) or laptop
Cable for controller
Tripod or stand (weights if necessary)
Neutral density filter
Glass cleaner (if shooting through a window)
Lens cleaner and tissues
Caution ribbon
Sign with contact info
Gaffer tape (much better that duct tape - leaves no residue)
Cable ties
Ziploc bags

Is media card empty?
Is the size and compression set properly for the expected number of frames?
Is the image in focus with AF disabled?
Is the white balance set to manual?
Is the exposure set properly?
Is the camera secure and protected from the elements (wind and rain)?
Is the power adequate (fresh batteries - reliable AC power)?
Is the intervalometer set properly?
Does the intervalometer have fresh batteries?
Is there dirt on the lens or the sensor?
Is the viewfinder covered (in the case of an autoexposure timelapse)?
Is the ISO speed set properly?
Did you add any Neutral Density filters if necessary?
If you plan on leaving the camera without surveillance, is it labeled and does it have your contact info on it?
Is the area around the camera off-limits to onlookers?
Did you do a short test run?