Best Tactic For New Adwords

It looks like you're new. Be prepared to lose your ass. I would recommend a bunch of keywords and bid low to avoid heavy loses. Of course try to bid a little more on keywords you think will convert but still bid low. Go through the searched keywords and start adding negatives / changing match types to avoid irrelevant queries. It's better to spend $30 and lose $30 than ending up spending $1,000 and losing $900.

I do not recommend starting with having lot's of keywords. Even with perfect campaigns, i dont recommend having thousands of keywords.

Each keyword has it's own psychology, when a particular user is searching that. We just need to understand that and keep that in mind while selecting a keyword.

I will recommend to start with 10 or more keywords to find out what is working for you.

One of my favorites (if possible) is to add location based targeting on top of geo targeted keywords that are exact matched.

Bid high for people that you know are in the right stage of the buying cycle, and once you have confirmed which keywords convert, you can open it up slightly. Remove keywords that suck from the search term reports. Repeat in another geo.

If you don't have geos, just start with the best exact match phrases and when you find the ones that are working, add them to another campaign that can find new converting keywords. Take out the good ones and move them to the exact campaign. This way you can control the exporatory budget (since they are separate campaigns).
This can be almost impossible if you don't have good product margins for ecommerce.