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 anengagement ring.

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!

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'.