I have (in vain most times) been trying to promote a strategy to defeat Hilary and Trump at the same time.
Most people I know are not fond of either of the two candidates running for president. They general fall into one of three camps. "I am going to write-in Mitt Romney or Ted Cruz" or "I will vote for Trump or Hilary because they are better than the alternative" or last and most certainly least, "I love Trump or Hilary because of ridiculous reason A, B, and/or C". This is addressed the former two groups. The latter group is usually full of myopic idiots that have lost the ability to reason.
The only way to avoid both candidates as president is if they are denied 270 electoral votes. The only way for both candidates to be denied 270 electoral votes is if another third-party candidate wins enough states to slim the pool of available Electoral College votes to under 270 electoral college votes. If this doesn't happen, we are guaranteed with Hilary or Trump.
The most common argument both the GOP and the Democratic party make against voting third party is that a vote for anyone other than Trump (Hilary) is a vote for Hilary (Trump). For the nations entire history now that argument has worked. No third party candidate has won even a single state in a general presidential election.
One reason why third party candidates don't win states is that there are always so many. There are 36 minor political parties and 5 minor political parties. In the vast majority of elections, th majority of voters generally pay attention to the first 2 parties. However, a couple to a few million voters always vote third party candidates. This year, given the choices, many people are looking at third party options. This is where the strategy lies.
The anti-Trump and/or anti-Hilary camps need to come together to support one third party candidate. With high unfavorability ratings for both candidates, there are obviously a vast majority of American's that are not happy with their choices from the GOP and Democrats. Sadly, a majority of those will choose one or the other to prevent the less desired choice from winning. However, there may be just enough who just can't bring themselves to fall-in with Hillary and Trump to out-number those that do vote for along GOP and Democrat party lines.
The problem is that they all have differing views and opinions. Many will write in the candidate they liked that conceded in the primaries, many Mormon's plan to write in Mitt Romney, and another group will choose the third party option that they most prefer. This will dilute the effect on the popular vote for an outsiders chance of snatching states and electoral votes from the GOP and Democrats. This would likely leave us with Hilary or Trump even though the winner may actually only win 50+ million votes out of 150 to 200 million votes.
However, if the voters that hate the power party choices vote for a single candidate, the third-party candidate could win some states and those states' electoral votes. Neither of the power party candidates will win the election outright. If this happens the House of Representatives chooses the Pres from the top three candidates and the Senate picks the VP from the top two candidates. If the House of Representatives cannot come to a winner the VP chosen by the Senate acts as President until Congress votes a winner and escapes the deadlock.