Try to visit people that you know are going to get a lot of traffic, but that are not going to die. For example, if someone says, "Investigate ____ tonight", you should probably infect the person they are going to visit, as the Investigator will bring the plague to other people.
Try infecting names that stand out in the beginning of the game. But be careful, as there could be a Bodyguard or Crusader that is going to protect them.
Werewolf strategies work well with this role - but make sure you don't visit the same target as an actual Werewolf as you will die.
If you are role blocked by an Escort/Consort early in the game, you can always claim Tracker as you would know who you infect every night.
Another strategy is to lay low (Maybe pretend to be Away From Keyboard) and wait until there are 5 or less players alive. Then start infecting. Becoming Pestilence should be easy, because there are only 4 or less people to infect.
Be wary that you do not wait too long, however, or you may be found by the Town and lynched.
Lookout is a good claim for this role, especially early on - You know who is infected, and players spread infection by visiting each other. By the same logic, Tracker is also a good claim.
If you are a TownInvestigative role that is told to check upon another person's role, you might want to refrain from doing so if you know that the Town is vulnerable in the case of a Pestilence (for example, the Town only has the same amount of Townies as there are all evil roles combine). However, if you think you are already infected, or if you think it is inevitable that a Pestilence will be coming soon, then you should continue visiting that person, as you would be helping catch Pestilence by narrowing down the pool of suspects.
The best way to stop Plaguebearer} is to kill them early before they become Pestilence. If you are a TownInvestigative role and you happen to find someone suspicious of being a Plaguebearer, it is not a bad idea to announce your suspicions of a certain person. Even then if the Plaguebearer becomes Pestilence, the whole Town will probably lynch Pestilence immediately. Announcing that you found a Plaguebearer earlier and then having them turn into a Pestilence makes your claim a lot more believable than if you just revealed it to the Town right when the Plaguebearer evolves.