Miss Perspicacia Tick is a witch and a "witch finder". She is from the lowlands but travels the regions which are hostile to witches looking for girls who have the potential to become witches because a person with the gifts of a witch but without the opportunity to develop them can be an unhappy, even dangerous, girl. Miss Tick makes her living as a teacher, a role which has given her the habit of correcting spelling, grammar and punctuation. As she says, "I am a teacher as well as a witch. Therefore I make lists. I make assessments. I write things down in a neat, firm hand with pens of two colours." She also earns her money by doing bits of medicine and misfortune-telling. Miss Tick does not look like an ordinary witch because looking like a witch can be dangerous when walking among the uneducated. She does not wear magic jewellery or carry a magic broom. Since she often finds herself in areas where witches are unwelcome, she has a spring-operated hat that only grows a point when she wants it to. The hat spring tends to stick because it gets rusty due to her being ducked in ponds so often.
Miss Tick's familial is a lawyer who has been turned into a toad which is one of the clues Tiffany uses to determine that Miss Tick is a witch. In European folklore and folk-belief of the Medieval and Early Modern periods, familiar spirits (sometimes referred to simply as "familiars" or "animal guides") were believed to be supernatural entities that would assist witches and cunning folk in their practice of magic - cats were common but toads were as well. Miss Tick's familial is likely to stay a toad since no princess ever kisses a toad, frogs being the favoured animal form for princes. The Toad leaves Miss Tick and becomes the lawyer for the Mac Nac Feegles.
Miss Tick had "twice been thrown in ponds", a real Roundworld test for whether a woman was a witch. If she floated she was a witch and was burned at the stake. If she sank, she was not a witch but drowned instead and went off to "heaven" - a better place in the eyes of the church who administered the test. In the eventuality that she does end up tied up and being thrown in a pond again or attached to a dunking stool by superstitious witch hunters, she has the advantage of her time at Quirm College for Young Ladies where swimming in cold water was considered character building and where she mastered the ability to stay underwater for prolonged periods of time. She also owns a book on escapology and spends her free time practicing untying difficult knots - shades of Houdini. Possibly the reason she must spend so much of her energy avoiding hate and harassment, rather than accepting donations of gratitude as other witches do, is that she is always travelling so never has the opportunity to build up a faithful clientele. Or it could simply be that she is not very likeable.
Since she has been educated at Quirm College for Young Ladies, in the company of people like Sybil Ramkin and Brenda Rodley (Dowager Duchess of Quirm) and other "ladies who organise", Miss Tick must come from a reasonably prosperous background. However, it is clear that as a witch-finder she doesn't make much money (in common with most witches) since she does such things as sending herself by post when she needed to travel by coach; putting stamps to the value of ten pence on herself, and declaring herself to be within the two ounce weight limit. (Though the clinching argument with the coachman was her pointy witch's hat, when she finally got the hidden point to unfurl).
Though she may not be considered one of the more powerful witches, she is an expert with a shamble. She may be a bit prissy but should not be underestimated. Miss Tick was sharp enough to capture Tiffany's imagination, and she knows her own limitations. Tiffany's adventure takes place while Miss Tick has gone to get help from two "edge witches".
In The Wee Free Men it is by means of a shamble that she discovers Tiffany Aching and that an incursion from Fairyland may be on the cards. She is quick to recognise some of Tiffany's qualities, even if she does not see all of them. Despite that fact that Tiffany lives on the chalk that neutralises most of Miss Tick's magic powers, she observes that Tiffany has both First Sight and Second Thoughts, has not only met the Feegles but been helped by them, and was able to see Jenny Greenteeth and stop her.. However Miss Tick did not pick up the possibility of Tiffany having Third Thoughts.
Joining the travelling Teachers, she started to teach Tiffany about witchcraft, and encouraged her to leave home to continue her training. "I don't teach people to be witches. I teach them about witches. Witches learn in a special school. I just show them the way, if they're any good." The thing about a special school was an idea that needed to be tested.
Tiffany absorbed a lot of sound knowledge from Miss Tick e.g. "Always face what you fear. Have just enough money, never too much, and some string. Even if it's not your fault it's your responsibility. Witches deal with things. Never stand between two mirrors. Never cackle. Do what you must. Never lie, but you don't always have to be honest. Never wish. Especially don't wish upon a star, which is astronomically stupid. Open your eyes, and then open your eyes again." Most importantly, she said: "Once you learn about magic, I mean really learn about magic, learn everything you can learn about magic, then you've got the most important lesson still to learn." "What's that?" "Not to use it. Witches don't use magic unless they really have to... We do other things. A witch pays attention to everything that's going on..." Miss Tick also tellls Tiffany: "Mistress Weatherwax says witches are people who look up." i.e. ask questions about things.
When she is up on the Downs by the remains of the old shepherding hut, Tiffany demonstrates that she has heeded Miss Tick's words when she says the following to the memory of Granny Aching: "I have got to go away. I... I've got to learn proper witching, and there's no one here now to teach me, you see. I've got to... to look after the hills like you did. I can do things but I don't know things, and Miss Tick says what you don't know can kill you." - the last comment definitely accurate.
Miss Tick is also a bit of an author, having penned the book "Magavenation Obitsis" Witch-hunting for Dummies (a play on the popular 'For Dummies' series of books which began with 'Dos for Dummies' in 1991) which she deposits in various non-witch-friendly villages. The book includes such useful advice as that you should drown rather than burn a witch, you should ensure that the witch has silver coins in her boots, and is given a nice meal of soup and tea before her ducking. She also wrote "Fairies, and How to Avoid Them", and "A Feegle Glossary", presumably for those who failed to avoid them as well as the "Bestiary of Transient Monsters".
In spite of her decidedly unwitchlike appearance, Miss Tick's name gives an obvious clue to her profession (Miss Tick - Mystic). Her first name is Italian for 'perspicacity' which means 'the quality of having a ready insight into things; shrewdness.' - appropriate given that she needs insight to identify potential witches.