Please Note that these are the best instructions for germination to the best of my knowledge, but there may be better methods available for some species, as some methods work for some people, while completely different methods sometimes work for others. The instructions mentioned here are either the methods I use for those varieties, or they are the instructions recommended to me by my supplier(s) when any instructions are provided.
Guide to Germination Requirements
Cold Stratification - Seeds need a cold stratification period before planting, or before germination can occur. Most temperate trees and shrubs, as well as some perennials either need a cold period or they will just germinate in slightly higher percentages if they are given a cold period. See instructions below for cold stratification guidelines. A good guide is if you are in doubt, give the cold stratification period, as it never hurts even when it isn't necessary, and it often speeds up the germination a bit.
Double Dormancy - Seeds have a double dormancy, and therefore they need a cold stratification period, followed by a warm period, then another cold period, and the seeds will germinate in the second warm period. Very few of my seeds need this treatment, but the three genera of seeds that I offer that do best with a double dormancy are Paeonia (Peonies), Magnolias (Magnolias), and Ilex (Hollies).
Soaking - Seeds benefit from being soaked in water (preferrably hot water) for 6 to 12 hours or so before germination will be optimal. Seeds can be soaked longer, but it is not recommended to soak most seeds longer than 24 hours. Basically any seeds with a moderately hard seed coat or any seeds that appear to be shriveled at all, will benefit from a soaking before you plant them. I actually use the system of when in doubt soak the seeds for a few hours before planting, as soaking is very rarely harmful and is usually a bit helpful.
Nicking - Seeds benefit from being nicked with your fingernail or being filed slightly to get through the hard seed coat. The seeds that need this treatment are any seeds with extra hard seed coats, or seeds that do not swell at all after soaking. The most notable species that needs this treatment are the aquatic Lotus (Nelumbo), as they have such hard seed coats that the seeds will never germinate if something isn't done to compromise the seed coat. Once again it is not usually harmful to make a slight nick on the seed coat of any seeds if you are in doubt at all, just do not nick more than to just scratch through the surface of the seed coat.
General Planting Guidelines and Instructions
Once any pretreatment methods have been accomplished, if there are any needed for the seeds you are planting, I simply use the rule of thumb of planting the seeds about as deep as they are thick (no deeper), which generally ensures that the seeds are planted at the correct depth, and I just like to use any good quality fine potting mix that is composed of peat, and vermiculite, but there can also be sand and/or perlite in the mix as well. Then simply keep the seeds and soil warm (figure on a temperature of 75F to 80F, unless a different temperature is noted for that particular species), and moist, but never allow the soil to dry out completely, or become soggy, the key is just maintaining a nice even level of moisture. Beyond that, simply be patient, as your seedlings should start sprouting in anywhere from less than a week for a few species to many months for some other species - Patience is very important when growing seeds. The only thing that I do beyond these instructions that seems to help is I cover the seed pots and flats with some type of clear plastic to keep the humidity up, which also helps to maintain the proper moisture level. Beyond that, good luck and have fun.
Cold Stratification Instructions
To accomplish the cold stratification needs of most species that benefit from or require such treatment, all that needs to be done is the following. First, simply mix the seeds with a small amount of moist (not dry or soggy, just lightly moist) peat moss, potting soil, or sand, and then place the seeds and medium in a bag and place it in the refrigerator or similar temperature location for a period of 30 to 90+ days. For most seeds, 30 days is enough, but longer is often slightly more beneficial. After that you are set to plant the seeds as described under the general planting guidelines and instructions above.
To accomplish the needs for seeds that have a double dormancy (such as many Hollies and Magnolias among others), simply administer the cold treatment as described above, then subject the bag with the seeds and medium in to a warm period where temperatures reach 70F to 80F for about 30 to 60 days or so, then give a second cold treatment the same as the first one. After this second cold period, simply plant the seeds as described above under the general planting instructions.
To soak most seeds that benefit from the soaking (such as Hibiscus, and many seeds with moderately hard seed coats), simply place the seeds into a container of water, and I find that it is beneficial to use water about as hot as it will come out of your kitchen faucet to start the soaking process and just allow it to cool to room temperature for the remainder of the soaking period of 6 to 12 hours. If the seeds have particularly hard seed coats, you may want to nick them first (see below) or allow the seeds to soak for up to 24, or until they no longer float (at least that is a common way to tell if seeds are ready to be planted, although it doesn't work with all seed species, just most of them). After the soaking period, simply plant the seeds as described above before they dry off completely.
To properly nick any seeds that have hard seed coats, such as some Mimosa species and particularly the aquatic Lotus (Nelumbo) seeds, you can use different methods to successfully compromise the hard seed coat to allow germination to take place. For larger seeds, such as the Lotus, you can use a file, or even a grinder if you are very careful as to not grind them too far, and for smaller seeds, a small file or even rubbing the seeds against something coarse such as a brick will work. Basically you want to just scrape through the outer layer of the seed coat, so you generally want to scrape until you see a cream or white color, or until you can just tell that you are through the outer seed coat. After the scraping, simply plant as described above, or soak in water briefly, then plant them. The only exception is for the Lotus seeds, which since they are aquatic plants, you just need to drop the seeds into a container of clean, warm water (the warmth is important for fast growth to occur) after you have scraped the outer seed coat, but remember to change the water every few days, and if everything goes according to plan, the Lotus seeds will sprout quite fast, and as soon as the seedlings reach a height of about 4 inches, you should transplant each one to a separate container, or they will soon be tangled together and you will do more harm to the little plants by taking them apart than they can stand, so it is very important that if you are starting several Lotus seeds at once, to transplant them quickly when they start growing. Beyond this, there may be further tips or advice out there, and some advice may even be better than these instructions, but these are the best instructions that have worked for me and are recommended by my sources. Good Luck, and Have Fun.