It depends on what you want to use your data for.
Here are the columns in my spreadsheet:
A ID - a number that I use to tag bags, tubes, reels, etc. (just goes from 1 up to ... n)
B Manufacturer - not always known
C Part Number - manufacturer part number
D Type - broad classification, semi, passive, hardware, etc.
E Subtype - more narrow classification, e.g. passive divided into resistor, capacitor, inductor (and also resistor array, resistor pot, resistor trimmer)
F Sort - Contains something to sort by. e.g. resistor, capacitor, inductor value, transistor Vceo, etc.
G Tolerance - List tolerance (for resistors, capacitors, inductors, voltage references, etc.
H Package - the package (TO-3, SO-23-5, etc)
I Style - mostly SMD, or through hole (TH)
J Description
K Data - Do I have the datasheet for this component
L Qty - quantity when purchased
M Qty Used - Quantity used
N Date - when the part was delivered
O Cost ea - Calculated from cost and original qty
P Retail Each - typical price in quantities of 1
Q Bulk each - typical price in larger quantities (qty originally bought typically)
R From - Where I got them from
S Part No - supplier's part number
T Location - My storage location
U Total (1) - calculated value of parts remaining at purchase price (inc freight)
V Total (2) - calculated value of parts remaining at 1 off price (not inc freight)
W Total (3) - calculated value of parts remaining at bulk price (not inc freight)
X Notes
Y Cost - cost of line item
Z Order - total cost of order including this line item
AA Freight - freight for this order
AB Accum Second level of accumulation
AC Freight Second level of freight
Sounds complex, but it allows me to locate parts quickly, list them in an order suitable for a first approximate search (to see if I have suitable or alternate parts), allows me to cost projects based on replacement cost of parts, and it gives me a total value of inventory for insurance purposes.
If you have different needs, you may require fewer, or different columns.
edit: I have added the column letters and 2 additional columns I have because I get my Sister-in-law to send me stuff sometimes where people refuse to ship outside the US or where they want *way too much* to do it (e.g. places that insist on using international courier delivery)