I use the acronym "MR.GOSEA" to remember the characteristics of life: maintain homeostasis, reproduce, grow, show organization in their structure, respond to stimuli, use or make energy, and adapt.
Maintain homeostasis: Organisms exert a lot of energy in keeping an internal balance. For example, organisms sweat when hot, breath harder when using oxygen during physical activity, release insulin when blood sugar increases, etc.
Reproduce: Living things pass on their genes to their offspring.
Grow: Living things add or repair cells throughout their lifetime.
Organization: There are levels of organization amongst all living things- organelles make cells, cells make tissues, tissues make organs, organs make organ systems, and organ systems make organisms.
Stimuli: Organisms respond to external stimuli.
Energy: Living either make energy (photosynthesis makes glucose and cellular respiration makes ATP) or use it (cellular respiration uses the glucose made during photosynthesis).
Adapt: Living things adapt to their environments. For example, if an organism lives in a snow-barren environment, then darker varieties will be more likely be consumed by predators. Over time, lighter, camouflaged varieties will be more abundant.