When the world doesn't end, you will either feel silly or claim you got your dates wrong.

That doesn't stop people like Robert Prechter. In June 2010, the gloomster pundit predicted the Dow would fall to 1,000. This week it hit a four-year high of 13,326.

Plenty of otherwise sober souls have been predicting a great share-price apocalypse ever since the first meltdown in autumn 2008. That wasn't quite the end of the world, although at times it felt like it.

There have been moments when I've been tempted to hunker down on a windy hillock and await the end of days. Judging by your comments below the line, I would find plenty of Foolish company up there.

The four horsemen of the apocalypse are still circling markets. Leading the charge is that tiresome old nag the eurozone crisis. You have to admire its staying power, if nothing else.

The fabled China "hard landing" is breathing hard at its shoulder, followed closely by the U.S. "fiscal cliff" (when the Bush-era tax cuts expire at the end of the year) and, finally, conflict in Iran.

There is also the rank outsider of a shock 40% currency devaluation by the Bank of Japan, much feared in China, whose export industries could get trampled in the stampede.

This summer could go one of three ways:

1. Muddling through
Somehow, the eurozone is glued together with another splodge of liquidity. China and the U.S. live to fight another day. There is an uneasy peace with Iran. Doomsday averted -- but investors remain wary.

2. Shock recovery
The European Central Bank loads up its big bazooka, and markets soar on a mountain of freshly minted euros. The U.S. consumer rides in to save the day, and the Chinese export miracle resumes.

3. Oops -- apocalypse!
Club Med electorates finally snap. The single currency splits asunder, and markets burn. The U.S. hits that cliff, and China goes the way of all property bubbles. Israel bunker-bombs Iran's nukes.

So which is it to be? Quite frankly, I don't know. You don't know. Ben Bernanke doesn't know. Nor do George Osborne, Mario Draghi, Francois Hollande, or even Warren Buffett. Nobody knows.

So how do you respond? You could simply leave all your money in cash, but that only guarantees that it will fall in value, in real terms.

Given three possible outcomes, I've developed a three-pronged response:

1. Saving a little every month
I've set up a direct to the low-cost unit trust HSBC FTSE 100 Index fund, which has a low total expense ratio of just 0.27%. Every month, the money buys more units in the tracker at the prevailing price. This means I don't have to worry what markets are doing. If they rise, I buy. If they bump along, I buy. If they crash, I buy.

As I'm only committing a relatively minor amount each month, I can't really lose.

2. Buying on the dips

This is a bit trickier. If the market falls 1% or 2% in a day, or a target stock falls 4% or 5%, it's very tempting to hang on one more day to see if it becomes cheaper still.

Still, I'm targeting blue-chip stocks yielding between 4% and 6% by topping up my holdings in Aviva (AV) , GlaxoSmithKline  (GSK) , Ladbrokes, Royal Dutch Shell (RDS.B) , and Vodafone (VOD).

If markets fall, I get that inflation-busting yield. If they rise, I get capital growth as well.

3. Keeping some powder dry
I'm not committing all my money. If the apocalypse does come, I want plenty of ammunition. As any Fool knows, a stock market meltdown is a great buying opportunity. It certainly was in March 2009. If there is another share-price apocalypse, it could be the buying opportunity of a lifetime.

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