just knitting a handy guide for all hand knitters!
Knitting Yarn
Knitting wool is very often NOT wool! This tends to be a general term for knitting yarn - which can be acrylic, cotton, linen, wool from goats, alpacas and different varieties of sheep, or even bamboo! Very many good yarns are a mixture of some of these, combining the best qualities of each. There is so much yarn on the market that it is really down to the knitter’s choice, not forgetting budget. 100% acrylic is cheapest and OK to machine wash and tumble dry. Yarn with any kind of wool in it will look nice and keep its shape well, but you may have to launder with more care. Cotton and linen can look superb and are cool in summer, but do not have the stretchiness of wool. Cashmere is lovely and soft! But expensive!
THICKNESS
When discussing yarn thicknesses, we talk about ‘ply’ - this means how many fibres are twisted together. For example, if you untwist a short length of four-ply yarn you will end up with four wispy fibres. Three and four ply yarn are used for summer-weight cardigans or jumpers, or newborn baby clothes. Double knitting (abbreviated to DK) is 8 ply and is the most common thickness for knitwear. Aran weight is slightly thicker for a more bulky jumper, and chunky is thicker still. The bulkier the yarn, the thicker the needles required.
AMERICA
In the USA, yarns are identified as fingering, sport and worsted going from thin to thick. My research in trying to give British equivalents shows there is some overlap, so if you are using American yarn for a British pattern or vice versa, it’s probably best to check your tension by knitting a small square. Knitting patterns give a tension guide which you should compare with your knitting.

Tension
Tension is key to the size of your knitting. For example, if you knit a square 20 stitches wide in double knitting, it will obviously end up much bigger than a 20 stitch square knitted in thinner 4 ply wool on the same needles. The ‘tension’ is different. Many types of yarn have slightly different tensions, too, even if they claim to be the same thickness! Other factors include the size of needles, and how tightly the individual knitter works.
Knitting patterns always give a tension guide at the start of the instructions. This is for the yarn recommended in the pattern, so if you are using a different one you should knit a square first to check your tension. You can then adjust needle size if necessary to get closer to the tension guide, but There is also often a guide on the label of the ball of wool, which you can compare with that given in the pattern.

Buying yarn
I love wool shops! The variety of colours and textures is so appealing I can’t help buying! Most have a bargain basket of odd balls and it’s fun to rifle through these and imagine what you might be able to make with them, especially if you can find colours that complement or contrast.
Sometimes you can find oddments in charity shops - worth checking regularly.
The internet is a boon especially if you don’t have a local wool shop. If you know what yarn you want, try eBay first in case someone is offloading it cheaply, then go to the many online wool suppliers - but bear in mind that postage costs may make it cheaper to shop locally if you can.