There are more free patterns available now than anyone could work through in a lifetime. The difficulty is no longer finding one – it is finding a good one, and telling the difference before you have bought the yarn.
Searching properly
Search by construction, not by appearance. “Top down raglan cardigan” will find you what you want; “nice cardigan” will not. Patterns are indexed by their technical terms because that is how they are written.
Include the yarn weight in the search when you already have yarn. “Worsted weight hat pattern” saves you from falling for a design you cannot make with what is in the cupboard.
Add the craft explicitly. A search for “blanket pattern” returns crochet, knitting, quilting and sewing results in one undifferentiated pile.
Judging a pattern before you commit
A pattern worth your time states its yarn weight, its hook or needle size, its gauge, and its finished dimensions. If any of those four are missing, expect trouble – not because the designer is careless, but because you have no way to substitute yarn or predict the size.
Photographs of the finished item on more than one angle are a good sign. A single styled photograph often hides the construction.
Check whether anyone else has made it. On pattern databases, a design with many completed projects has been tested by strangers in a way an unmade one has not, and their notes will tell you where the instructions are unclear.
Free versus paid
Free patterns are frequently excellent. Plenty of designers release good work free and sell the more complex designs.
What you tend to get with a paid pattern is more sizes, tested instructions, and someone to ask when a row does not work. On a large project in expensive yarn, that is often worth the price of a skein.
Finding a pattern you half-remember
This is a common problem – a blanket seen years ago, a bootie from a magazine long since thrown out.
Describe the construction rather than the look: how it was built, what the distinctive stitch was, roughly when you saw it. Craft forums and pattern-search groups are good at this, and someone usually recognises it.
If it came from a discontinued yarn brand’s leaflet, look for the brand’s archive. Several keep their old patterns online for free.