Viego is a life steal maniac with an amazing passive that you always want to use it gives a short unattackable state along side with a hefty heal after its done, so make use of your life steal to keep you alive while targeting low health characters, do not focus tanks that will get you killed. Early game strategy should be focus up being aggressive against low health characters takes give a little leeway and high ranges lure them out most will likely hide in the turret though.

The mid game is very important to establish your strength and how the enemy will engage you if you got fed in the early game then you are in luck because they ill fear you and you should take this time to target turrets and lower their defenses if you haven't attained that fear yet then roam around and focus killing their small health characters and farming. Late mid game try to focus the dragon and helping your allies.

By this point you should be able to murder anyone and everything so you should be good but don't get to cocky and get locked down in heavy team fight make sure your always targeting the backend first. You want to eb and flow through the map making sure you stay unpredictable and keeping them unfocused on one location but if you need to lure them out focus the top lane and push it hard.