The nature of the Apokalypsis, with parts of the game board disappearing, short-term tactical reactions are usually more important than long-term strategic plans. The two basic strategies are 1) spreading the risks by spreading the meeples and 2) gambling by gathering the meeples. Spreading the meeples may help you survive but unless you gather your meeples, you're not likely to have the most meeples left when the first player gets eliminated. Thus, gathering your meeples is generally wise, if it can be done without losing them on the way that is.
Which tactical considerations should you have in mind then? You need to stay away from unsafe tiles but how? Let's start by looking at the information you have.
Each turn you draw 2 omen cards and returns 1. That give you the following information:
Something will happen on the 6-12 hexes noted on the chosen omen.
Something is less likely to happen on the 6-12 hexes noted on the returned omen.
Something may or may not happen on all the other hexes.
That's certainly not very useful. You can avoid the hexes in 1) but that will exclude up to 1/3 of the board and you'll still not be safe! To make use of the information, you must use deduction and card counting.
For the deduction, much can be deduced from the other players' movements. There are only 8 different omen cards, meaning that there are 8 specific "slices" of the island that can be affected. Learn them by heart! With that knowledge, observe the movements of the other players' moves carefully. Does a player completely vacate the Eastern area? Does someone moves along the middle circle (the "Earthquake area")? The former indicates that the player just chose the East card and the latter that the player just returned the Earthquake card.
Consequently, the moves of your own meeples shouldn't be too obvious. If you want to vacate East, also vacate say Earthquake. In that way, the other players won't know which of the the two omens you chose.
The Card Counting
For the card counting, you can observe which omens that are revealed in each apocalypse and consequently shuffled into the bottom of the pile. Since each omen only has 2 cards, the return of the first East omen will make Eastern tiles a bit safer and the return of the second East omen will make Eastern tiles absolutely safe. Of course, the East omens will eventually reappear. Hardcore gamers may want to count the number of omens that may be drawn before a specific omen reappears but usually it's enough to count with 1-2 safe rounds from the time when the first East omen was shuffled into the bottom of the pile (the more players, the less safe rounds).
By combining the deduction and the card counting, you should be able to form a pretty good idea which areas that are safe and which that are unsafe during certain points of time.
Aggressive vs Proactive Play
How to use this information then? Moving to the next safe area each turn is one answer but too passive and reactive to win you the game.
A more aggressive play is to push other meeples to unsafe areas. This is particularly strong if you can push opponents to hexes affected by the omen card you're about to choose and have them discarded. If given a choice, choose meeples of the leading player first and of the player before you in turn next (to give them less chance to move back to safe hexes).
A more proactive play is to plan two safe areas ahead. Do you have an open path to the next safe area? Do you need to build a bridge or two? Do you need to set up a blocking position to prevent other meeples from pushing you or occupying the hexes before you? The images below show some tactical positions to consider.
The meeples are denoted with colored circles; filled in the hexes they stand in and hollow in the regions they moved from.
White's meeple in the has no land routes left. A bridge opens up an escape route for it.
Keep the right omen
Yellow has just kept an East omen and moved away her last meeple from East. From that move,
Blue concludes that East is dangerous but there is no space left in the hex that Yellow escaped to.
Instead, she stays in the East but keeps an Volcanic Eruption and escapes the hexes near the Volcano.
East+Volcanic Eruption triggers an apocalypsis at the hexes that Blue just left and also returns
the East omen back to the bottom of the pile. Blue should be safe her yet another turns.
Block your opponents' escape routes
Black is in the lead and wants another color to be eliminated so that the game ends. By moving
across the bridge towards the Volcano, she creates a path of two adjacent full hexes.
This means that
those meeples cannot be pushed (Red is a neutral color in this example) and that the Yellow meeple
south of the Volcano cannot move. If black can trigger an apocalypse with South+Volcanic Eruption,
Yellow will be eliminated and Black win.
The End Game
The opening and mid game should typically see proactive play whereas aggressive game becomes important in the end game. Either you bash the leader or, if you're the leader, look for opportunities to eliminate the weakest player and claim the victory with the most surviving meeples. Remember that in case of a tie, you'll win if the player was eliminated in your turn!