Love poems work best when they are written from the heart. Do not follow clichés that you think express love. Consider the person or people you love and be honest with how you feel about them, but do not be afraid to take artistic liberties.
Love is not all wine and roses, it is also about how you feel about the person, how nervous you are when you are around the person you love and how you enjoy being around her even in the most mundane of situations. Let how you truly feel for her come through in your poems.
Do not feel like you always have to rhyme. Sonnets and haiku can offer great structure for your love poem, but above all love poems are about inspiration. Be creative and allow your true feelings to be voiced, even if they do not fit within the rigid parameters of any particular form.
Many poets have dedicated their poems to someone in particular by titling their poem after her. This is sweet, but not always necessary. Consider being abstract in expressing your love to her. Oftentimes this can be a lot more expressive than spelling out the obvious. For example, “I love Claire/ I love her shiny auburn hair/ I will buy her an éclair” may be very true, but it is not the most romantic of sentiments.
As in all poetry, love poems should flow off the tongue with a pattern or a rhythm. Read your poem out loud while you write it to make sure it sounds as beautiful as it looks on paper.
Who says your love poem has to even be about a person? Maybe you love and want to write a poem about a tree, or the family pet or your car. If these poems come from the heart, you have no reason to keep them inside.
Be creative when writing your poem. Consider unusual rhyme schemes (if any), abstract word choices and other devices.
The most important part of writing a love poem is to let it be true to your emotions. Write about what you love, and you will love what you write.