Spanish uses a lot of diminutives and the Real Academia Española has some rules to form them; check them out.

1. One-syllable words

a) ending in a vowel: pie (foot) – -ececito, -ececillo, -ececico, -ecezuelo: piececito.
b) ending in a consonant or y: rey (king) – -ecito, -ecillo, -ecico, -ezuelo, -achuelo, -ichuelo: reyecito.

2. Two-syllable words

a) ending in e, ia, ua, io, ei, ie, ue (in the first syllable): calle (street), reina (queen) – -ecito, -ecillo, -ecico, -ezuelo, -achuelo, -ichuelo: callecita, reinecita

b) ending in n and r: joven (youngster), amor (love) – -cito, -cillo, -cico, -zuelo : jovencito, amorcito

3. Three or more syllables

a) ending in n or r: imagen (image), comedor (dining room) – -cito, -cillo, -cico, -zuelo : imagencita, comedorcito

b) any other ending: animal – -ito, -illo, -ico, -uelo: animalito

These are general rules, but there are plenty of exceptions, so listen carefully for them.