For the identification of the species belonging to the Poaceae family one has to to study in depth the main features of the flowers of this family, which are very small, without petals, and have characters that are quite difficult to interpret for a beginner. In the Poaceae, the flowers are gathered in structures called 'spikelets', which are in turn arranged in inflorescences of different types. The different forms of these inflorescences are quite easy to appreciate. We distinguish three main types:
Digitate: the inflorescences consist of several linear spikes diverging at the top of the stem like the fingers of a hand:

Other species have a single spike at the top of the stem, with sessile or very shortly stalked spikelets:

In some genera, such as Lolium, the spikelets are widely spaced, and appressed to the stem with their narrower side..:

...whereas in the genera Elymus, Elytrigia and Agropyron they are appressed to the stem with their broader side:

In other species the spikes are dense and cylindrical...:

...or oval:

The third type of inflorescence is the raceme (or panicle), in which the spikeletes are clearly stalked:

Some inflorescences in the Poaceae family may be of difficult interpretation. For example, in the genus Dactylis the spikelets are crowded in very compact panicles (the inflorescence is not a spike, since at least the lower part of the inflorescence is clearly stalked):

In other cases the panicles are long and narrow and the spikelets have a very short stalk, which makes the confusion with true spikes possible. Usually these species can be reached selecting both options: