I'd say no never prick the sausages if you can help it. the fat inside helps to keep them succulent and moist, and if you have a problem with the splitting and are pricking them to release the pressure as was stated by @foodrules, then I'd say you are cooking them over too high a heat. Lower the heat, or if you are BBQing move them further from the source, then you will get to have unsplit, moist sausages. When pan frying I prefer a very low heat for a long time. This allows a delicious sticky crust to develop on the outside of the sausages. mmm...
If they were meant to be pricked why would they not come pre pricked?
I'm assuming you're wanting to make classic dried sausage such as the salamis and saucisson of Italy and France.
Common salt is certainly the key to the drying process and a quarter pound per 10 pounds of meat is a pretty commonly used ratio, but you must also use a curing salt which helps protect against some of the truly nasty food poisoning bugs such as Clostridium botulinum. This just loves the warm, oxygen-free centre of a curing sausage and produces the botulinum toxin which kills around 5% of people who contract the illness.
Sodium nitrite (often called pink salt) or sodium nitrate (Insta Cure #2 - which converts to nitrite over time in the sausage and the nitrite then does the actual curing) are two commonly available salts.
One-half ounce per 10 pounds of meat in addition to the regular salt is a commonly-used ratio. Don't use more and be sure to keep it away from kids and your regular salt - in quantity it is very dangerous.
Something else I always use in dried sausage (but not hams or bacon) is a live starter culture such as LS-25 or one of the various stains sold as Bactoferm. Added to your mix at two ounces per 10 pounds of meat with say three ounces of dextrose sugar and they will feed on the sugar and excrete lactic acid (just like the bacteria that you add to milk to make yogurt). This lowers the pH of the sausage which makes it even harder for dangerous bacteria to grow. It also produces that delicious acid tang to fermented sausage. If you use this, you hang the sausage in a really moist warm place for the first 24 hours to give the bacteria you added a head start (I have a tall old box with a lightbulb in the bottom).
As far as temperature and humidity goes, 60F and 70 percent humidity are ideal. Humidity below 60 percent can dry out the casing and meat surface too fast which can then harden and prevent the centre from drying (which will then just rot). You could try hanging the sausage above a bowl of water to increase the general humidity in the room.
Your sausage is ready when it has lost at least 30 percent of its original weight. Dry white mould on the casing is good, fuzzy black and green is bad. If you see a little you can rub it off with a cloth dipped in strong brine. Any sign that it is more than just on the surface and you'll have to bin the sausage and start again.
So to recap. Chill your 10 pounds of meat and mince it to your taste. (at least 20% fat gives good texture and flavour). Dissolve the LS25 in a little water and then add it, a quarter pound of salt, a half ounce of Insta Cure #2, up to a couple of ounces of spice of your choice (ground chilli and paprika for chorizo or fennel for something more Italian) a half ounce of finally chopped garlic, a glass of red wine and mix it really well. Then stuff into soaked casings, pricking out any air bubbles with a pin. Hang in a warm place for a day to get the good bacteria you added going, and then hang them in a cool, dampish place until the sausages have lost at least 30% of their weight.
I hope I haven't put you off - it's really as simple as baking a cake and homemade dried sausage is a tremendous thing of joy and beauty - but you really must get the ratios of salt and curing salt right.
If you want to be safe and make fabulous cured sausage I can absolutely recommend Cooking by Hand by Paul Bertolli and Charcuterie by Michael Ruhlman & Brian Polcyn which are both available in the US and Europe from Amazon.
But please don't eat your current batch. Throwing it away won't hurt like paralysis that starts with the face and slowly descends to the rest of the body, bringing death by respiratory failure...
Best Answer
You need to let the sausages sit exposed to some air -- refrigerated, of course -- for a few hours (preferably overnight) so that the twisted segments of casing dry out and become tough again. Lay them out on a baking sheet, uncovered, and flip them at some point to make sure the whole surface is drying. If you have space, you can hang them up so that all sides are getting air at once. (Aside: this is also an important step for smoked sausage. See "sausage pellicle".)
If you don't have time for that, you can tie off each twist with a bit of butcher's twine (although this is also time-consuming and rather mind-numbing). One loop, cinched tight around each twist, will keep them from untwisting in the water. If you're really pressed for time, stuff the casings a little tighter and don't link them at all. When these full-length sausages have cooled, you can simply slice them into your desired portions.
Also, if you're losing "a lot of juices", you are either overcooking the sausage or not emulsifying it properly. There should be very little juice exuded when you cut into a link. You need to keep the ground meat quite cold during every stage up until cooking. The sausage should become quite tacky after mixing -- enough that it actually sticks to a rubber spatula (although some variation is possible for stylistic reasons). Don't boil the links, either, when it comes to that stage. Poach them in (salted) water in the 180-190˚F range, and check them with a thermometer -- they don't need to go higher than 160˚F (former "safe pork cooking temp" recommended by USDA). I shoot for 145-150˚.