1. Remember that most couples will go through it one time or another 2. Communication, communication, communication. Deal with the issue together openly. If you BOTH want to address it, there will usually be a "work around" 3. Patience and understanding 4. Take the pressure off yourselves 5. Compromise - on both sides (to state the obvious) 6. Remember that in most cases it's temporary - there will be ebb and flow
Look at the reasons it might be low. Is she unhappy, has she got a lot of stress going on at the moment, are you pulling your weight around the house and with children, do you make her feel valued, cherished, loved? Talk about it and don't stop even if it's uncomfortable, you both need to know how the other is feeling.
Is there a particular reason for it? (I'm thinking possibility of small children, completely knackered) or has this always been the case. If it is simply that she is totally shattered by the end of the day can you do more to help out? I know when my DCs were small that there were times when sex just felt like one more sodding thing on my 'to do' list for the day.
For me having small DCs meant I was drained at the end of the day, emotionally and physically (think sorting constantly bickering DCs on a rainy day, often through gritted teeth whilst trying to keep your temper, very tiring).
Then there's the resentment as DH breezes in from an interesting day at work but expecting a quiet evening whilst you read bedtime stories.
By then, sex is not on my mind, partly through tiredness and partly through repressed anger that DH isn't doing his share.
DCs now long since left home, workload at home is minimal, I am def more interested in sex now when there is a fairer balance and more me time.