If it's Nevermore you want, you're not getting better advice from anywhere other than 2009 himself. Watch me. (And other 2 in the series so far)
If it's about any hero, it has many factors. One of the most important ones are getting used to your hero's attack animation and, if you're playing competitively, which I'll assume here due to your 1st post, to have map awareness not to get killed by roaming VSs, CMs, ESs etc. Also, carrying TPs to get to a better farming position, escape from incoming ganks. Utilizing neutral creeps to the most of your extent. Support players in your team are also a big factor as they need to protect you properly if you're on lane like morph vs. invoker, hence dual/tri lanes.
With nevermore you HAVE to farm once you've died, make it imperative to regain the 30 souls, unless there's like a teamclash 5 meters from you. In the start if you're dominating a lane, stay on it and try killing the opponent as much as possible. While he's dead try to get a few ganks off. If you're losing your lane, focus on ganking or getting your teammates to help you gank the opponent, never forget that SF is a hero which can regain his farm that he lost in 10 minutes in mere 2 minutes due to insane flashfarming abilities. Also, it's always useful to kill a few neutrals when you're waiting for a gank, creeps on your lane are pushed too far, enemy ganker is waiting near your lane. After some 10 minutes however, nevermore needs to start controlling the game, that's when his razes are the most powerful and ganks are your primary concern, however, you still need your bkb/dagger and try not to join fail ganks like support heroes have to, only the ones you know will succeed, just farm till an opportunity arrives. But don't overdo it. SF farms fast, you're not dusa, you don't perma-farm. If there's a teamclash when you have 60 souls, you're in it, no questions asked, especially if it's around that period, you're by far the strongest hero in the game (especially if you won your lane), utilize your power. Later on pushing lanes around is a useful way to farm as you go as SF does it incredibly fast. Just one hint that I see many players do wrong: if there's a fight late game and creeps are pushing into your base, you don't go defend, SF is one of the strongest teamfight heroes in the game, and must always be present in one.
Well, that's in short what I could write about SF. I've been playing the hero in a semi-competitive environment for a long time now and this is what I can share from my knowledge, hopefully some hints were useful. Still don't forget to watch 2009's advices, he's surely better than me