Proper preparation is important: cleaning, cutting, etc. is easier to do before freezing a product than after defrosting it -- e.g. as is also coating mushrooms with breadcrumbs. Take a look at your freezer manual, which often contains valuable information from the manufacturer. Additionally, there are numerous websites on the internet providing detailed advice.
Should I first blanche the vegetables or not? A truly difficult question to answer. A certain amount of nutrients will get lost during the blanching process. On the other hand, the remaining nutrients (because the enzymes have been deactivated), colour and flavour will remain longer.
Shock Freezing Process
Make sure the product is frozen as quickly as possible, as this is where most of the quality is lost (slow growing ice crystals will destroy the cell walls, thus, damaging the texture: fruit will become "mushy"). Turn the machine on to full freezing power a few hours before (do it the day before if the freezer is very full). Do not freeze large packages and fill bags as flat as possible. Do not put them on top of each other for freezing. You can always rearrange them later. Do not freeze too many things at once. Note: you can buy frozen products at the supermarket.
Regulating Storage Temperature
Set the storage temperature at a minimum of at least -18 °C, maybe even lower. This way, almost all food should keep for about 10 months when packed appropriately. A longer storage period would not really make sense, as freezers are not intended for keeping foods for times of need or emergencies.
Refreezing defrosted food? Basically not a problem from a microbiological perspective, if the item in question is only slightly thawed or the defrosting period was short. Bacteria do not generally reproduce at freezing temperatures, so you do not have to fear that refreezing could damage your health. However, the quality loss could be considerable.
Do not underestimate the influence of packaging: unsuitable or very thin materials could let oxygen or odours through. Make sure the package is sealed as tightly as possible after removing most of the air (lack of air-tightness or too much air will lead to freezer burns and dry out the surface. While this is not dangerous, the quality will deteriorate.) Vacuum-packing and sealing is ideal, but a knot in the tightly twisted end of the bag should also do. A wire paperclip should not be used. Only use tins if they stay sealed when frozen and can be filled almost to the top. Do not freeze goods with strong odours such as onions or garlic. This could have a very negative effect on the cake you have frozen before.
Last but not least, label and organise the contents of your freezer to keep track of everything.