How much should I be feeding the lil' guy?

Depends on what you are feeding him, how active he is, what is his current condition over/under weight according to a vet.
 

I agree with the above. It depends on the brand of food (however many calories are in a cup) and activity level primarily.  

Let me expand on my answer.  For example if your dog is a good weight as determined by the vet and the dog is gaining weight you should cut back on the amount you are feeding the dog.  If he is underweight and losing weight then increase the food intake.  If he is overweight cut back on the food.  How much to feed depends entirely upon the dogs body condition.
 
If you feel guilty that you don't think the dog is getting enough even though the weight is good you can supplement the meals with carrots, green beans or canned pumpkin (unsweetened).
 
Steve.
 

I'm almost afraid to ask,but what food are you feeding? As everyone else has mentioned,k/cals need to be known,energy levels etc etc.
You couldnt feed the same amount of  food with 500k/cals per cup,compared to one with 300k/cals.

I've been wondering if there are any broad guidelines on kcals/lb for dogs, as there are for people (I vaguely remember something like 13 calories / lb for an inactive person to 18 calories / lb for a very active person).  Are there any broad guidelines like this for dogs ? 

JoAnnDe--
 
In general, a moderately active dog should consume approximately 2% of his/her body weight in k/cals per day.  For example, a moderately active 10 lb. dog should consume around 200k/cal per day.  If your dog is more active, feed more--less active, feed less.
 
My 14 lb. shih tzu is fairly active, and I feed him approximately 2.5% of his body weight per day, sometimes more (anywhere from 350--380k/cals), depending on his activity level for the day--he never eats the same amount from day to day.
 
My friends, shih tzu, on the other hand, leads a quieter life, he's 15 pounds---she feeds 300 k/cal (2%) .  He could probably be fed a bit less, as he is a wee bit stout.
 
I do think most dogs fall into the moderately active category

I feed Eukanuba.  They have been on it all their life.
 
I wouldn't get too hung up of the calories per cup stuff.  Feeding is easy.  Feed them enough to keep them in a good body condition.  Actually a little lean is better than a little fat unless they are old dogs.  I do look at calories when feeding treats to know how that would affect there overall daily intake.  When most folks feed their dogs they forget to take into account snacks.

I want to add that the correct feeding amount is usually less (sometimes substantially less) than the recommendation on the bag.  As mentioned by timsdat--treats must be taken into account and really shouldn't be more than 10% of the diet. []

Holy cow - I'm going to completely change my mindset !  By the looks of it she should be getting (at 12 lbs of body weight) approximately 240kcals / day.  That's about 1/2 can of the Pinnacle food OR 1/2 cup of the NB Duck&otato dry .... I've been giving her 1/2 cup of the NB PLUS 1/2 can of wet !  and it looks like NOTHING to me and she always acts like she's starving.
She's only been with me since Jan 20th, and she was free-feed the first two weeks (and ate about 1.5 cups of the NB a day !).  She did gain about a pound in the first two weeks so I knew I should cut her back .... plus I wanted to start adding wet food .... plus I wanted to get her on a regular feeding schedule.
She's on the new regimen about a week now.  Since her fur is finally growing in (she was shaved to the skin when she was at the rescue org) its hard to tell what's going on with her weight by looking at her.
 
That leaves the scale.   I'll weigh her today and keep close tabs on her weight changes .... unfortunately that means I'll have to weigh MYSELF also (since the only way I can really get her weight is to weigh us together) - ugh, does that count as an "ultimate sacrifice" or what ? LOL

JoAnnDe--
 
How old is your dog?   Oscar ate way more when he was young than he does now (he's a bit over three now).  Also, you should be able to gauge your dog's body condition by feeling her---here's a quick guideline:
 
How to Recognize If Your Dog Is Overweight
A good method for evaluating the body condition of your dog includes observing and feeling his body. Researcher, Dottie La Flamme DVM, PhD, designed the following system that helps owners identify potential obesity in their pets. This nine-point system defines ideal condition as one in which the dog's ribs are easily felt and the waist and tuck-up (the belly area between ribcage and rear end) are discernible without being prominent. The dog in ideal condition has a thin layer of fat over the ribs.
1. Emaciated: Dogs with ribs, hips, and other bones protrude and are visible from a distance. Emaciated dogs show a loss of muscle as well as an absence of body fat.
2. Very thin: A step up from emaciated; bones are visible but not as prominent and muscle loss is slight.
3. Thin: Ribs and top of spine may be visible and the pelvic bones prominent. (Some breeds are naturally thin, so don't be fooled at the bony appearance of Salukis, Afghan Hounds and other sighthounds.) Waist and tuck-up are evident.
4. Underweight: Some fat on the ribs; visible waist and abdominal tuck-up.
5. Ideal: Ribs are easily felt and have a thin layer of fat. Waist and tuck-up are obvious but not exaggerated.
6. Overweight: Ribs have noticeable fat; waist and tuck-up are discernible but not prominent.
7. Heavy: Ribs are covered with a heavy layer of fat and noticeable fat deposits appear on the spine and
at the base of the tail. Waist is absent or barely discernible.
8. Obese: A heavy fat layer completely obscures ribs and heavy fat deposits appear over he spine and around the tail base. Waist and tuck-up disappear.
9. Morbid: Massive fat deposits in the chest area, along the spine, and around the tail base. No waist or tuck-up. Abdomen protrudes, and fat deposits accrue on legs and neck.
 
If she feels like an ideal weight, she may need the amount of food you are currently feeding.  Just watch her and lessen the amount fed if she feels portly.
 
I personally like to keep my dog a bit on the lean side--he's healthy and active.

According to my vet most of the dogs that they see are rated 7 or 8 on that scale.
 

The basic rule of thumb is to look at the condition of the animal to guide you. The reccomendation on the bag or can are just guidelines. Some dogs require half of that and some double (or more).

If you stand over you should see some indication of a 'waist', not a complete cylinder or sausage outline. When you run your hand over the ribcage it should feel like the bones on the back of your hand between the wrist and knuckles. The knuckles would be too skinny and and ribby, so further down toward your wrist where you feel the bones but generally they are not prominant and the flesh is well covering them.

Also kibble is dehydrated unlike fresh food, so it doesn't seem to look like much volume to our eye, it's deceiving. Generally, a whole can of wet food is about equal to a cup of kibble calorically in many brands (not all but most).

According to my vet most of the dogs that they see are rated 7 or 8 on that scale.

 
Yikes!

Prancer is 8 months old, so yes, I do think that her caloric needs are higher at this stage, but I'm giving her double the "normal" calories so I think the weigh-ins are needed to ensure that I'm not overfeeding her.  
When we adopted her on Jan 20th she was definitely a little underweight (using the descriptions above) at 12 lbs.  Since her fur has started growing in its much harder to determine her rib prominance.  I can feel them when I run my fingers along her sides, but I have to press a bit to feel them through her fur (which is really dense and about 3/4" long now) and I'm having a hard time determining the right amt of pressure needed to "just touch" her ribs to get a good check on her.  She was up to 13 lbs 2 wks ago and that was probably her ideal weight (give or take a few ounces) so I'll monitor to make sure that she doesn't fluctuate from that too much.
Wouldn't it be nice if you could enter a dogs height, leg length and body length into a calculator and get an "ideal weight".   At we human's have that one (thanks to the insurance companies !) - we may not like what they say, but at least they give us a starting point !