Your running shoes should fit with the following key points in mind:

• Toe room: There should be about a thumb's width (roughly 1 cm) of space between your longest toe and the front of the shoe to accommodate foot expansion during running. This usually means choosing a shoe about half a size larger than your normal shoe size

• Heel and midfoot fit: The shoe should feel snug but not tight around your heel and midfoot to prevent slipping and blisters. When you hold the back of the shoe and try to lift your heel, there should be little to no movement

• Width: The shoe should fit comfortably on the sides without squeezing or allowing your foot to slide side to side. Choose wide or narrow options if needed to match your foot shape

• Lacing: Tie your laces snugly but not too tight to secure your foot without causing discomfort. The shoe and foot should feel like one unit without pressure points

• Fit check: When standing, press your thumb next to the ball of your foot and toes to check for adequate space. Also, check that the shoe’s eyelet rows are parallel, indicating a proper fit

• Additional tips: Feet can be different sizes, so you may need to size shoes accordingly. It's best to try shoes on later in the day when feet are more swollen to get an accurate fit

In summary, running shoes should be snug in the heel and midfoot, have enough toe room to prevent crowding, fit your foot width properly, and be comfortably secured with laces to support your running style and terrain