Does prayer work? Most of us assume it does, even if we don't really understand how. If we pray for a fine day for the church barbecue, does God really readjust the weather patterns over the Atlantic so we don't get rained on? Does it mean someone else's barbecue gets rained on instead, and what do they think about that?

There are bigger questions, too: what about prayer for healing that isn't answered? Or what about prayer for healing that is answered – great, but why doesn't God heal everyone?

Most of us are prepared to leave the answer in the realm of mystery, and hope and trust that God knows what he's doing. And that's fine, though there are good answers to these points. But it isn't wrong to ask questions about prayer, because thinking about it can save us from serious mistakes. Unless we really dig down into what the Bible says about it, we can end up with misconceptions that prevent us praying effectively – and open us up to a world of disappointment.

So here are some of the things we need to be careful about with prayer.

1. We can trivialise it.

In his letter to the Philippians, Paul tells them "in every situation, by prayer and petition, with thanksgiving, present your requests to God". It's sometimes translated, "Pray about everything." Some do. Every situation is brought before God, even down to finding a parking space.

But a good rule for reading the Bible is always to look for the context – and here, the context is anxiety. The sentence is introduced, "Do not be anxious about anything" and it's followed by "And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus" (Philippians 4:6-7).

In other words: when we are anxious we should pray and God will hear us. It's like a child who's frightened of the dark – his parent will run up the stairs and comfort him.

But children grow up. And if we are Christians with any degree of maturity, we'll have learned how to cope with the bad stuff. We'll have developed the right reactions and the right Christ-like character to be able to do the right thing and take responsibility for our own behaviour.

When we pray, we're asking God to change the world for us. And perhaps sometimes we need to cultivate an acceptance of the present moment, with its discomforts and irritations, and not be so needy. Part of growing up is learning to live with disappointment and frustration, and realising that it's OK not to have everything we want.

2. We can abuse it.

Some preachers teach a 'prosperity Gospel', that God wants all his people to be rich – like Creflo Dollar, who hit the headlines last year when he asked his followers to donate $65 million for a new, top-of-the-range private jet. 

This is obviously wrong. But there are other ways of abusing prayer that perhaps aren't so obvious. For example, often teachers on prayer encourage us to be specific in what we ask for. But the danger in being too specific is that we end up telling God what we want, rather than letting him tell us what we need. Prayers can sound as though we're giving God orders.

At their worst, this kind of prayer can be used as a weapon. Someone who prays that her minister will be given the gift of preaching more interesting sermons probably has an agenda of her own.

There are other dangers too. If there's sometime we feel passionately about – maybe a huge moral question like abortion or euthanasia – it's easy to assume that God's on our side. It's easy to find ourselves praying other people will see things our way.

But we can't co-opt God into fighting our battles for us, no matter how worthy the cause seems. God is free. We abuse prayer when we try to use it to preach our own opinions.

3. We can mechanise it.

Apparently once five young students were spending a Sunday in London, so they went to hear the great 19th century pastor Charles Spurgeon preach. While they were waiting for the church to open, a stout, bearded man offered to show them round: "Would you like to see the church's boiler room?" Out of politeness they agreed. He took them down a stairway and quietly opened a door. On the other side was a room with around 700 people praying inside. "This is our boiler room," he said quietly, before introducing himself: it was Spurgeon himself.

It's a great story. The idea is that what happens in the church service is powered by what happens in the prayer meeting. But is it really true that the more people pray, and the more intensely they pray, the more likely God is to answer?

I believe that God is free to do what he likes. If he chooses to pour out revival on a congregation after 700 people in a basement have prayed for it, he will. If he chooses to do it when it's just one, and she isn't too sure about the whole business, he will.

Of course there can be a connection between intense, believing prayer and God's action. But there's no necessary connection. God is not moved by the numbers of people praying. He is not more likely to answer prayers if we gather for prayer at five in the morning, either, or if we go without food while we're praying. That's not how it works.

It isn't what we choose to do that matters. It's what God chooses to do. It's all too easy for us to imagine prayer as our side of a bargain, requiring a response from him. But we cannot bribe God or coerce him.

The Psalmist says, "Sacrifices and offering you did not desire, but my ears you have pierced" (40:6). The reference is to a servant who is offered his freedom but chooses to stay with his master; the master will "take him to the door or the door-post and pierce his ear with an awl" (Exodus 21:6).

Prayer can be the equivalent of sacrifices and burnt offerings. It's good, but we should never imagine that it binds God in any way. Far more important is the deep-down relationship of trust and commitment. Our ears have been pierced; we are marked as his, whether he answers our prayers or not.

That doesn't mean prayer meetings are pointless. But what God chooses to do in response to our prayers is up to him. It's not a way of putting pressure on him, it's a way of putting ourselves at his disposal. What he wants to see in the one who prays is the broken and contrite heart.

Mark Woods is the author of Does the Bible really say that? Challenging our assumptions in the light of Scripture (Lion, £8.99). Follow him on Twitter: @RevMarkWoods