ya i did it once.. that really a great joy to set up google shopping feed..
Let me try to explain step by step process..
1) set up google merchant account
2) after set up and log in you have to go to "[FONT=arial, sans-serif]
Data Feeds[/FONT]" option
3) Now click to "New Data Feed" tab
4) select targeted country (Where you can show your data feed)
5) Select "Format" (googlebase is Recommended)
6) Now "Data feed filename" (enter data feed file name that you will save with while you create a feed file afterword)
Ok now once you entered all these details you can see the "Data Feeds" dashboard
Now move to you Feed Creation.. How to create feed?
This Data Feed you have to make in Excel Sheet.
First of all ask to your developer or if you are a developer urself then run a query in database to collect all products..
IDs - it means simple numbers like 1, 2,.... so on..
Titles - title of every product page
Descriptions - Description of every product page
links - Product page urls
price - Price of each product
availability - In Stock or out of Stock
mpn - ex. 1-TP307-07307
image link - Link of each product's image
brand - Brand name of the each products
condition - New or used
google product category - this is specific and pre defined tab so you have to select category from here
product type - which type of product is yours Ex. "Men's wear"
gender - Male or Female
age group - ex. Adult
Once you complete with this naccesory things Save As your Excel sheet in Txt formate and save with the same name (mentioned above in Step no. 6 ) you put while in creating data feed in google merchant account
These things you must requried in terms of make feed for more details you can check out this url
Ok now when u Done with data feed again go to Google merchant account and in "Upload" section select "Manual upload" option and upload you txt data feed file.
If all steps you follow correctly your feed will be live within 24hrs...
Hope this will help you out
PM me if you have any query.