I personally do number crunching to see if the there is anything odd in the balance sheets (as i understand) and that basic ratios are what i want it to be.(ROCE, ROE, D/E ratio) .
1.) I also use DCF model, and instead of looking at the exact value i get out of DCF what i do is to keep a +-10% window and then invest.
2.) Sometimes i look at the business and try to understand the mgmt's view and i only invest in business i can understand (That's why there isn't a bank in my portfolio).
But i really try hard to to see if the business is under valued.
TVS motors: I picked up TVS about 2.5 yrs ago(if i recollect well) and it was almost nacent for a long long time.
When i did the number crunching i figured that the intrinsic value was almost in the range of what the stock was trading at but the business was really something that could sustain for a long time and i could see it grow. Hence invested.
Hope it helps