As a general rule, 6" cans are placed 6 feet apart, 5" cans are placed 4 feet apart, etc. The cans are positioned so they are centered over the edge of the counter's edge to reduce shadow when you are standing at the counter. Under cabinet lighting can also help reduce shadows. You'll also want cans centered over walkways. And depending on the size of the room, you might need some filling in the middle (I have an island with two pendants, so no need for cans in the middle). I have 4" cans which I am happy with. The smaller cans allow more flexibility in customizing your lighting.

I wish you had more time to put together a real 'lighting plan.' Lighting is so critical in the kitchen. I hope this helps a little.

I usually go with the 6" cans to take advantage of the excellent Cree CR6 LED lamps that use only 10 watts each, put out good quality light, and last just about forever. They're sold at Home Depot under the Ecosmart brand for $40 each (or 4 for $150 on their website), and that price includes the built-in trim rings which saves about $12 that separate trim kits usually cost, so it's like the bulbs are more like $28 each, about what you'd spend for two or three 65-watt halogen floodlamps that the LED will still outlast.

I start them about 12" from the wall cabinets, about 6 feet apart. If you like 4" cans surrounding the cabinets, HD sells a 4" version of the aforementioned LED modules for $50; alternatively for lower cost you could go with 5" cans with PAR30 halogen floodlamp bulbs, or 3 to 4" cans with low-voltage MR16 bulbs if you like the really small ones; space these slightly closer together. Halogen MR16 bulbs have excellent color rendering, although they use more electricity and don't last as long as LEDs.

Luv2Laf and Lee 676 - many thanks for the general information. The electrician plans on putting 6" cans about 3 feet apart and that seemed too close to me for such a large can. I appreciate the general rule and will address it today.

I would never install cans 6' apart! That is way too far a spread. 4' is ideal for a 6" can. Remember- you can always dim away light, but adding it is tough. I like to stay 16" away from cabinets (roughly 12-13" from crown). Try to place lights where they will be on either side of a main work space such as a light 2' off center on each side of the sink. This way your sink is illuminated from the side rather from right above where your body will create a shadow. Seriously consider pre-wiring for under cabinet lights. I went with LED pucks from elementalLED.com and I could not be happier.

As far as the cans go, I would recommend 6" cans with CREE CR6 LED bulbs. They are fully dimmable and use little power. As mentioned by Lee, they come with the trim ring and can be had for $25-40 at HD (depends on if your local utility has a rebate on them- I believe Ct still does but LIPA stopped theirs). They can be used with a regular $6 can.

oops...As a general rule, 6" cans are placed 6 feet apart, 5" cans are placed 5 (not 4) feet apart, etc.