Pick up where you left off, or alternate. The important thing is to set a goal and then stick with it. It is like loosing weight, or bodybuilding, or exercising. If you want to loose 30 lbs in six months you set a goal, make a diet and cardio plan and then stick to it. When you change your lifestyle completely then you keep yourself in shape.
The same is true with spirituality. At first it may be hard, but if you have the drive and the stick-to-it-ness needed you can do it. Make a time every day to get out your Bible, find a quiet place, and read. Remember, just like weight training, someone doesn't make huge muscles going into a gym and lifting huge weights once or twice a year. They get it by being consistent, week after week, month after month.
If you want to exercise your spiritual muscles, if you will, you need to be consistent and stick to it. It is better to read five minutes a day than two hours one day and then stop for three months.
I myself always started at the beginning and read through to the end. But I'm a completionist. Once I start something I won't stop until I'm finished with it, I'm just that way. Some try starting with Psalms. Perhaps alternate, read a chapter in the Hebrew Scriptures, a Psalm, a Proverb, and then a chapter in the Greek scriptures, I did it that way once. There are 150 Pslams, so that will keep you going for 150 days. The Proverbs are deep and usually require meditation and research to fully understand, so I never really liked the idea of reading through the Proverbs in a short period of time. So splitting it up throughout your year, if you stick to a plan of reading the Bible in a year is a good idea.
The important thing is to set a goal, you can probably find some excellent Bible reading schedules online if you don't have time to make one yourself. Print it out stick it on the wall, your billboard by your computer, next to your bed, wherever and then stick to it. If you miss a day or two, just make it up, but don't loose heart.
Also, it is pointless to read the Bible without the right heart condition. How many people have read through the Bible countless times without ever learning the truth? Prepare your heart, say a sincere prayer before you begin to read (you need holy spirit to understand what you are reading, and you need to pray for it before you read, not just after), focus on the material, and ask yourself what you can learn from what you read about Jehovah, his love for mankind, and how you can imitate him more in your daily life with others, your family and friends and neighbors. When you finish conclude with prayer. If you find a hard spot and want to research it, keep notes right it down, and if you have extra time then do the research.
One year, when I was 14 I keep the Insight books next to me as I read through the Bible and looked up every Bible character and place as I ran across them, as well as looked up each Bible book before hand to get an overall view of them. That really increased my Bible knowledge, and helps me to this day. Hope some of this advice helps.