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A tip for those using Foodsaver or other home vacuum packing devices:If you have sous vide tips or tricks of your own send them our way and we'll help you share them with everyone else.
If you want to seal something containing liquid such as a marinade, go ahead and fill the bag, but put it upright in the freezer for 1-3 hours (depending) before you seal it. You're not trying to freeze the entire contents of the bag solid. Your goal is to freeze water-based liquids and/or solidify fats just enough that they won't be sucked into the vacuum packer when you seal the bag.
If you use this method, be sure to thoroughly clean the part of the bag to be sealed (the neck of the bag, in other words), and clean it inside and out, BEFORE you put the bag in the freezer. Otherwise stray liquids will freeze onto the neck of the bag, and will interfere with the vacuum packer's ability to make a good seal.
You can now place the sealed semi-frozen bag into your at-temp cooking water, but most temperature controllers will try too hard to get the water back up to temp and will overshoot. Instead, you may want to put the semi-frozen bag into water that is deliberately cooler than the desired cooking temperature (10C/20F cooler seems to work well). That will allow the controller to bring the food and the water up to the desired cooking temp in a reasonable amount of time, but with little or no overshoot.
Lastly, note that for items such as seafood requiring very short cooking times, you will need to adjust the cooking time upwards from what is in the recipe to account for the time needed to get the colder food up to temp. Or you may wish to -- within food safety limits -- let the now-bagged food come back to room temp before cooking, and just put it in already-heated-to-cooking-temp water as usual. For longer-cooking items (multiple hours or days), on the other hand, there is really no need to adjust for starting with colder food/water.
Hope this info helps someone. Use/edit it to your heart's content. Credit me or don't, I'm happy either way.