Erotic stories can be a great way to communicate your desires in a subtle way. Buy your lover a sexy book that includes the kink that turns you on, and ask them to show or read you the bits they like (if any) out loud.
Alternatively, if you're confident that your lover will be open minded, be direct. Ask if there's anything new they'd like to try and tell them what appeals to you. By listening to your lover's desires, being non-judgmental and considering making their dreams come true (assuming you don't find their kinks a turn off), you're more likely to get a positive response to your own penchants.
Before any form of BDSM (bondage, domination, sadism and masochism), however mild, set a safe word. This is a word you wouldn't usually use during sex (some people like to use 'no' and 'stop' during kinky play as part of a 'scene'). Many people opt for a traffic light system with red meaning stop, amber meaning slow down and green meaning 'go for it'.
Keep play safe, sane and consensual. This means reading up more on any safety guidelines (almost ever kink has safety info online), avoiding doing anything while either partner is under the influence of drink or drugs and only exploring things that you both want to.
Kink can be a wonderful way to add spice to your relationship, building intimacy, acceptance and trust. Approach it in the right way and who knows where it might lead.