How can I identify ionic compounds?
You can do a series of tests.
Melting and Boiling points
Ionic compounds have high melting points (> 300 °C) and boiling points (> 800 °C). Solid covalent compounds have low melting points (<200 °C) and boiling points. Many covalent solids tend to decompose if they don't melt or boil by 200 °C and you continue heating above that temperature.
Solubility in Water
Most ionic compounds dissolve to some extent in water. Most covalent compounds tend to be insoluble in water.
An aqueous solution of an ionic compound will conduct electricity. An aqueous solution of a covalent compound will not conduct electricity.