Sand is a bad choice. It discourages drainage and aeration. There is essentially no reason to ever add sand to a potting mix. Beyond that, here is my advice concerning soil...

In general, I follow very simple "recipes." These recipes don't need to be very exact, but they are intended for good growing conditions (bright light, warm weather). When you start buying more challenging/expensive plants it is worth trying to do some research on individual the species you are interested in. The secret to success is taking these basic recipes and adjusting the particular ingredients for different conditions and locations.

One to two parts drainage material to one part organic material:
Good for leaf succulents. It is perfect for Crassulas, Sedums, Aloes, Echeverias, and most other leaf succulents. The vast majority of plants you could buy in big-box nurseries (Home-Depot, etc) will do well in this mix.

Two to three parts drainage material to one part organic material:
Good for stem succulents. Euphorbias and Haworthias both like this more freely draining mix. The majority of Cacti would do well too.

Four parts drainage material to one part organic material:
This is what to use for really touchy species. Anything that people say is prone to rot should be planted in this. Lots of caudiciform and pachycaul plants (Pachypodium for example) want this extremely fast draining mix. There are a surprising number of plants that actually do best in 100% drainage material!

Important note: All plants tolerate more drainage material better than less drainage material.

Organic material:
Peat moss is pretty much the devil. It compacts easily, holds too much water, actually *repels* water when dry, and to top it off isn't environmentally sound. Whatever you or anyone else does, don't ever use peat moss! Organic compost (composted wood, composted bark, and forest humus) is without doubt my personal favorite. You can get 1.5 cubic foot bags at my local nursery for about $10. Coir (pulvarized coconut husks) is gaining in popularity, and can be found at most garden store here in the U.S. If you go for coir, make sure you use the ground up kind instead of the stringier shredded stuff. If all you can get is the stringier stuff, just be really carefully to thoroughly break it up and mix it in to avoid a compacted soil.

Occasionally, if it is on sale, I will buy peat free commercial "cactus mix" but ignore the almost insignificant amounts of drainage material they include and just consider it pure organic material. In reality, organic material isn't needed so much to provide nutrients but instead to just hold water and release it in a controlled way. Contrary to the dominate advice, the best time to water a succulent is just *before* the soil dries out, not after. If the drainage material remains slightly damp, but not soggy, that "watering window" is extended by quite a bit.

Drainage material:
For this you are usually limited to what is available at the local nursery or hardware store. However, some good choices are pumice, crushed/decomposed granite, pea gravel, cinders/lava rock, pearlite, and orchid bark. In the ideal material, every single piece would be between 1/4 and 3/8 of an inch. The more jagged the pieces, the better the drainage and resistance to compacting. Pumice is great, but unfortunately it is almost exclusive to the west coast. You can find it for sale on eBay, but it is pretty expensive. Very well stocked feed stores will carry huge bags of pumice marketed as "Dry Stall". The pieces are a little smaller than optimal, but it is still a good find. Also, look for gravel sold for landscaping at nurseries and hardware stores. That is typically where I get mine. Pearlite is good, but I think it is too messy. It also doesn't hold up over the lung run if you intend to reuse your soil. Keep in mind that the more porous a material is, the more water it holds. Pumice and pearlite actually hold enough water that I always toss in extra to offset the effect. For a cooler, more humid region, a non-porous material like pea gravel will probably do the best.

Adjustments are pretty much made by adding more drainage material to a standard recipe. If it is colder than ideal, add more drainage. If it is darker than ideal, add more drainage. If it is more humid than ideal, add more drainage. Depending on exactly where your plants are and what your weather is actually like, you might find 2 parts drainage to 1 parts organic to be the minimum. Again, remember that plants tolerate more drainage material better than less drainage material, if in doubt, just add more drainage. It will also take some experimentation to find the blend you are most happy with.

I would argue that sand is not bad, but you have to use the right stuff. It must be irregularly shaped and it must be course sand, not fine playground sand stuff. You are looking for very course silica sand or swimming pool filter sand (this is hard to find as a lot of swimming pool filters are using crushed glass). All of these suggestions are opinions and what works for each individual. I personally think that 1/4" to 3/8" drainage material is excessively large, especially if you are mixing it 4 to 1 with organic material, and even worse if you are potting in 3" pots like I do. 3/16" is about right and will not compact around the roots. If you get the fine stuff that sticks to your hand when you touch it, it will just compact around the roots or settle to the bottom of the pot and clog the soil. I have linked you to a discussion in the Container Gardening Forum for Al's mix for succulents. It calls for a mix of various things like vermiculite and Turface. Vermiculite and Turface (or OilDri, which works as well) are excellent for drainage material. Shapes are irregular. They both hold water and nutrients and release as needed, and neither stays soggy wet. The rest you can find in the other post.

Here is a link that might be useful: Al's formula for Succulent Soil Mix