So you've decided it's time to pop the question - congratulations! But now comes the slightly tricky part... the engagement ring.

Making the decision to propose to your partner, no matter how long you've been together, is a huge leap in the relationship and the last thing you need to stress about is how to buy an engagement ring.

That being said, it's one of the most important purchases you can make, so feeling confident and at ease is important. We've come up with an easy, step-by-step guide that will answer every question you could possibly have when it comes to buying an engagement ring, leaving you to acutally enjoy the process.

Before You Buy:How do I know what style she likes?

Look at her day jewellery: Take mental notes of the jewellery she already wears and what her style is like. You'll be able to tell a lot about a woman by the day jewellery she wears as it helps you decide the bling-scale of the engagement ring. By doing this you'll know if she's a traditional bride or a girl who would want a more alternative engagement ring.

Ask her friends: A woman’s best friends will always know what style of engagement ring she will want. Whether it’s a feminine marquise cut diamond or a bold emerald stone, they'll have an idea!

Pay attention to hints: As friends and family members get engaged, watch out for your girlfriend’s comments on the rings that are given. It’s a really good way of piecing together her dream ring.

How do I find out her size?

Steal a ring: Take one of her day-to-day rings and use a ring sizer to measure it, or take it to your local jewellers to get a ring size.

Buy a distraction ring: If she wears jewellery casually, buy her a distraction ring that she can wear day to day and use the size of that to determine her size – this allows you to figure out the ring size without making her suspicious of the engagement.

Choosing the Diamond - Shape

The diamond shape is really important because it will define the overall look of the engagement ring you buy. There's 12 main shapes when it comes to diamonds for an engagement ring:

The different shapes of a diamond

1. Round

Round brilliant cut diamonds have a certain sparkle to them that's enhanced by the cut. It's a more traditional shape for a diamond and is extremely popular for engagement rings.

2. Radiant

The radiant cut diamond has a square shape with cropped, flat corners - it's a really unique design for a diamond and is perfect if your other half likes quirky jewellery.

3. Oval

Following a similar style to the round diamond, the oval shape and facets in this design allow more light to pass through, giving it an extra sparkly finish.

4. Emerald

If your partner likes a vintage style of jewellery, consider the emerald cut diamond. It's stylish, sleek and is made from a technique which was originally only used to cut emeralds.

5. Princess

The princess cut diamond is another really popular choice for engagement rings. The sharp, square cut looks gorgeous on its own, but is also really pretty when put alongside other princess cut diamonds.

6. Pear

Otherwise known as the teardrop diamond, the pear shape is much more unusual. It's a more quirky take on the round brilliant cut diamond and is perfect if your partner wants something a little different.

7. Trillion

The trillion cut diamond, also known as trilliant cut, is a triangular-shaped sparkler which is more commonly used as an accent stone - but looks gorgeous standing alone on an engagement ring too.

8. Baguette

The baguette diamond is a slim, rectangular diamond which look really gorgeous either side of an emerald cut diamond. The slim shape will give the engagement ring a unique twist that's not commonly seen.

9. Heart

The heart diamond is perfect for the hopeless romantic. It's perfect for a girly girl and takes a really skilled cutter to create the exact symmetry needed to perfect this shape.

10. Cushion

Often referred to as pillow cut diamonds, the cushion shape is similar to a princess cut, but with much softer edges.

11. Asscher

Similar to the radiant cut diamond, the asscher shape has more step-cuts to it, giving it even more edges for the light to bounce off - making it a really sparkly design!

12. Marquise

Last, but by no means least, comes the marquise diamond shape. It's stylish, chic and is also referred to as a navette, meaning 'little boat'.

How do I know how much to spend?

A traditional take on buying an engagement ring is that it usually costs around three months’ salary, but you definitely don’t have to stick to this. The budget for the ring should be an amount you feel comfortable parting with. Once you know the shape, style and metal of the engagement ring, it makes it a lot easier to shop around for good prices and much like when a woman is looking for a wedding dress, when you find the one - you'll know!

If you feel 100% confident that you know what you’re doing, then venture out alone to buy the ring. However, if you're less sure, take someone with you that she trusts like her sister, mum or best friend. Even though this has to be your decision, it’s always good to get another person’s opinion.