In freely spoken Finnish, and often in informal writing too, possessive suffixes have largely disappeared, except for some sayings and special contexts. It is normal to say mun auto, where mun is a colloquial form of minun. Similarly, instead standard Finnish hänen autonsa, we often say sen auto.
In public speech, possessive suffixes are still required. However, effectively as a concession to common practice, the rules of standard Finnish traditionally say that possessive suffixes can be omitted from some expression that express family relations and immediate environment relations. Examples include meidän äiti (our mother) ja teidän kylä (your village). The expressions meidän äitimme and teidän kylänne are possible, too, in written prose, but they have a more formal tone.
The colloquial usage actually often promotes clarity, since possessive suffixes often cause case suffixes to be omitted. For example, the noun forms auto, auton, and autot all become autoni, when the possessive suffix ni is added.
The loss does not extend to phraseological use or possessive suffixes in adverbs in words like mielellään (∼ mielelläni etc.).
In some contexts, Finnish uses neither a possessive suffix nor a personal pronoun. For example, the word äiti (mother) can be used standalone, leaving it to the context to determine whose mother is referred to. This applies both to standard language and to spoken language. It is of course possible to say äitini or mun äiti, but the simple äiti is more common unless there is a particular reason to make the reference more explicit or the context is formal.
It is also common to say and write e.g. Nostin kädet ylös (I lifted my hands), though Nostin käteni ylös is somewhat more common in written language. Omitting the suffix is not particularly colloquial in such expressions.