Monocot	Dicot
SEED
Monocots have only one seed leaf inside the seed coat. It is often only a thin leaf, because the endosperm to feed the new plant is not inside the seed leaf.	Dicots have two seed leaves inside the seed coat. They are usually rounded and fat, because they contain the endosperm to feed the embryo plant.
GERMINATION
Homeria                   Lilium                   Gloriosa When a monocot seed germinates, it produces a single leaf. It is usually long and narrow, like the adult leaf. Even when it is quite a round shape, there is only one seed leaf in a monocot.	Eryngium             Sanguisorba             Cladanthus When a dicot germinates, it produces two seedleaves. They contain the food for the new plant, so they are usually fatter than the true leaves. The first true leaves are often a different shape.
LEAVES
Washingtonia               Clivia                     Canna       The leaves of monocots are often long and narrow, with their veins in straight lines up and down the leaf. Sometimes, the veins run from the centre of the leaf to the edge, parallel to one another.	Malva                       Rosa                   Campanula Leaves of dicots come in many different shapes and sizes. The veins go from the central midrib to the edge of the leaf, crossing and joining to form a netted pattern all over the leaf.
STEM & ROOTS
Stem                     Sheath                       Root The stems of monocots are usually unbranched and fleshy. They do not grow thicker from year to year. New leaves often grow wrapped in a protective sheath formed by the older leaf. The roots of dicots are usually short and stringy. Dicots often have bulbs.	Stem                     Stipule                     Root The stems of dicots are usually tough. They can grow wider each year and are often branched. They sometimes have stipules at the base of the leaf. The root is often a single long tap root with smaller roots growing from it.
FLOWER
Cyrtanthus                 Pleione                 Agapanthus The parts of the flower of monocots are in threes. The sepals are often the same colour as the petals, making it look as if the flower has six petals. There are usually the same number of stamens as petals.	Oenothera               Epilobium               Geranium The flowers of dicots usually have flower parts in fours or fives. The calyx is a separate ring of sepals under the corolla, and is usually green.
SEEDPOD
Iris                   Anthericum            Hedychium The seed pods or fruits of monocots usually have three parts. The seeds are often large and fleshy. The largest seed in the world, the Coco-de-Mer, and the smallest seeds in the world, Orchid seeds, are both monocot seeds.	Lychnis                 Erigeron                   Clitoria The seedpods or fruits and the seeds of dicots are very variable in shape, size and texture. The seedpod can have any number of chambers, from none to many. There are often more seeds in a seedpod than in a monocot seedpod.

There's more about these differences and similarities here.