Peek is a variant of Osmosis, and differs only in the initial layout: in Peek, the four reserve piles are fanned out and their contents are fully visible. This allows you to plan ahead, something that’s not really possible in Osmosis because the reserve piles are squared and their contents hidden.
Peek (and Osmosis) are unusual for their foundation rule, where playable ranks “sift down” from higher foundations to lower ones. There isn’t too much room for strategy, but you’ll be kept busy keeping track of which cards can be played to which foundations. Expect to win around one game in ten or a bit more, if you’re good at paying attention.
The top foundation is special because there is no other foundation above it: you may play any card to it (if the card is of the correct suit).
If a foundation is empty, you may start it with a card of any suit you choose provided the suit hasn’t been played to any other foundation yet. The card’s rank must still obey the osmosis rule.
As a convenience, Solitaire Till Dawn X will allow you to change the order of the cards in each foundation if you wish. It may help you, for example, to keep the foundations in King-to-Ace order to make it easier to see which ranks have already been played. But it’s entirely up to you; the order of the cards within the foundations has nothing to do with the rules or with winning the game.
In some games you may be able to avoid getting stuck by playing the suits to the empty foundations in a different order. In the above example, if the first foundation is (say) Clubs, then the stacked Queens will get you stuck if you start the Diamonds foundation before (that is, above) the Spades foundation. But if you start the Spades foundation first, you might be able to win the game.
One trick that might be useful is to avoid playing three cards in a row from the discard pile. This helps ensure that you will see at least some different cards on your next trip through the deck.
Perhaps the most important thing is to simply pay attention. It’s surprising how easy it is to miss a possible play.