Basically what it says on the tin. When we speak about the experiences of the common man or woman in that period (and to be sure, wiggle room is fine, just keep it High Middle Ages please!) what are we basing that on? How much source material survives today? What is the weight between written sources and material remains?
How much variance do we see by location? Is there a great imbalance between what we know about Aquitaine versus England versus Burgundy?
How representative do we judge it to be, both within the region of those sources, and cross-regional as well?
If you're from Western Europe, one of our sources is Parish rolls. If your Church has avoided any great calamity since the 12th Century, then some of these records may well be extant. Parish rolls can tell us when you were born and who your parents are, if you got married, and if you had children, and when you died and what from.
As to your day to day life, we do have a couple of literary sources which do shed some light on the situation. One of the most common types is the Book of Hours. Books of hours were an incredibly popular form of religious text, even for the lay populace, which contained a series of important psalms, prayers and Bible verses. As the name suggests, the Book of Hours also contains a schedule for the hours of the major religious offices, as well as a calendar of major festivals, holidays and Saints' days. In many cases, these calendars were illustrated or annotated with whatever tasks and duties a dutiful labourer should be undertaking in that month: when to plough, sow and harvest, for example, or to say that over winter, farmers should look to weaving baskets, and repairing their houses and roofs.
One particularly enlightening source is Ælfric's Colloquy, an Anglo-Saxon to Latin phrasebook written as a series of dialogues between eager students and the workers, tradespeople, merchants and labourers they might encounter in everyday life. While this isn't a High Medieval source - it dates from the 10th Century - the roles therein are unlikely to have changed significantly in the intervening period. A 'conversation' with a ploughman, for example, goes as follows:
Ploughman: Master, I have to work so very hard. I go out at the crack of dawn to drive the oxen to the field and yoke them to the plough. For not even in the bitter winter would I dare to stay at home for fear of my lord; but, when I have yoked up the oxen and fastened the plough and the ploughshare to the plough, then I must plough a whole field or more for the whole day.
Teacher: Have you any mates?
Ploughman: Yes, I have one boy who drives the oxen with a goad. He is hoarse from shouting and the cold.
Teacher: Do you do anything more during the day?
Ploughman: Yes, indeed, I do very much more. I have to fill the stable with hay for the oxen, water them and take their dung outside.
A more back-and-forth conversation with a fisherman tells us how he sets out with traps and his boat to catch "eels, pike, minnows and dace, trout, lamprey and any other species that swim in the rivers, like sprats", cleans them and takes them to sell to townspeople at market.