There are two parts to successful investing: finding the winners and avoiding the losers.

But looking just for the former, especially if you focus mostly on revenue and earnings, can leave you exposed to the latter.

In order to fully benefit from your winners, you need to spot the ones to stay away from. After all, a 200% gain is completely wiped out by four other picks dropping 50% each. As for that winner, revenue and earnings are not the place to see trouble coming in time to do some good. You don't want to wait for an ugly earnings surprise that gives your stock a massive haircut before getting out.

That's why just about the first thing I read is the balance sheet. This is where the company's financial health is found and where sickness' warning signs often show up.

One balance sheet tool I like is the cash conversion cycle. This shows how fast the company turns its cash into inventory, sells that inventory, and then collects the cash on those sales. It's measured in days and, generally, the lower it is, the better. (For details on how it's calculated, check the Foolsaurus investing wiki entry.) It is possible to have a negative CCC, as Dell showed to great effect for several years. Seeing CCC increase can mean it's a company to avoid or exit.

This metric doesn't apply to every industry, however, such as banks. It's primarily for companies that interact with suppliers and customers, buying from one, selling to the other.

Here are three companies operating in the same industry that recently caught my eye:

Company

CCC (TTM)

1-Year Change

3-Year Change

5-Year Change

PetMed Express (Nasdaq: PETS)

24.4

(7.9)

(12.8)

(16.3)

PetSmart (Nasdaq: PETM)

44.6

2.0

7.7

14.5

MWI Veterinary Supply (Nasdaq: MWIV)

49.1

1.1

2.4

N/R

Source: Capital IQ, a division of Standard & Poor's, and author calculations. TTM = trailing 12 months. All numbers are in days. N/R = not reported.

Pets and pet supplies are a moderately fast cash cycle business. Without retail locations, PetMed Express has an advantage over PetSmart for CCC, as you can see. Still, PetSmart has been holding steady over the past year, though it's allowed CCC to creep up compared to just a few years ago. Hopefully, they'll be able to get a handle on that as we come out of the recession.

Of course, the cash conversion cycle should not be the end of your research, and it's best to follow trends over time. However, it can provide useful pointers to either getting in or staying away.

Go past the obsessive focus on quarterly earnings, and you'll be way ahead of the vast majority of the market's individual investors. By learning to calculate and use the cash conversion cycle, you'll more likely spot a deteriorating situation early enough to either avoid the company in the first place or get out before the company "surprises" with a bad earnings report.

PetSmart is a Motley Fool Stock Advisor recommendation. The Fool owns shares of PetMed Express. Try any of our Foolish newsletter services free for 30 days.

Fool analyst Jim Mueller, who works with the Stock Advisor newsletter service, doesn't own shares of any company mentioned. The Fool's disclosure policy has cycled through the company three times while you read this article, showing off on a unicycle.