First sector and then stock. There are broadly 3 phases in investing life (I have lived all 3, not sure if more left)...Basant jee is there anymore ?
phase 1. When one acts based on broker/friend. In this phase silverline looks more compelling as compared to INFY. This is learning cycle. More you lose money earlier you get out from here. This is quite diversified state.
phase 2. This phase starts after a considerable gap. Here, you remember your dark past. and try to pick all solid companies. You look at PER, BV, dividend yield and management etc. Here you are not loosing money but you are also not making multi-baggers (you wanted). Sometimes you don't get even index return. Sometimes you think that phase 1 was better given a little luck (as by then all you picks in phase 1 might be multi-baggers). This is quite diversified state.
phase 3. This phase starts immediately after phase 2. Here one try to bet on sectors & management. By this phase you are aware of many scripts and market functions. Here you apply what you learnt from earlier phases. You not only pick phase 2 type of companies in identified sectors but also you pick phase 1 type of companies in same sectors yet you feel quite relaxed. This is moksha state (no more birth/deaths, no more buys/sells). This is quite concentrated state.
I have lived every word of these 3 phases. I reached phase 3. One has to traverse all the way from phase 1. God bless all.