Make sure that she knows. Be verbal about it. Most men don’t feel comfortable expressing their feelings verbally or think that it’s not manly; which, to be honest, is a stupid excuse. Tell her what you like about her and encourage her in things that she likes to do. Ask her about her opinion on anything that she is interested in or should have a say in it.
Listen to her carefully and show interest. Don’t try to find solutions to problems that she should face herself. It’s very likely that she has already fought about the problems that you want to solve and is just trying to find sympathy. Just show that you care and you will always be there.
Show your appreciation through action as well. Cook for her and help around the house. Notice when she is tired and try to relax her or give a massage or just ask her to relax and let you do the working. Be sensitive to times when she is stressed or sick and try to be as helpful as you can be.
Give her gifts. Even small ones that don’t have much of a monetary value. Never forget anniversaries that she cares about. Have quality times and alone times where you just speak and watch TV or play games together. Also, small acts of kindness or gifts when they are not expected are far more impressive that you can imagine.