Planning
Before attempting to create a Wildflower meadow, there are a number of factors which should be given due consideration. From the outset it should be fully understood that wildflower meadows do require management and regular cutting is an important part of how to create a wildflower meadow.

This will include several cuts during the first year to a height of around 3.5 to 4 inches followed by further cutting, albeit less frequently in subsequent years as the competition from weeds and grasses is gradually reduced. It is also important to realise that cuttings will need to be removed from the site following cutting.
The next step to consider is the suitability of the site itself. The two crucial factors are soil fertility and soil type.
Soil fertility is best predicted by the past use of the site. eg. If the site has been under intensive farming, it is likely that the soil fertility will be too high due to past applications of fertiliser. In which case it may be necessary to deep plough the site bringing the infertile lower levels of soil to the surface and burying the topsoil. An alternative method, is to strip the topsoil altogether but if neither method is possible then a special Wildflower mix for Fertile soils may be required.
The next consideration is the soil type. If possible measure the acidity of the soil. This can easily be measured with a small pH indicator kit available from most garden centres.
Finally, an assessment should be made of the basic soil type. The main types being:

Loam typically light crumbly soils ph 6 to 7.5
Clay – typically heavy sticky soil ph 6 to 7.5
Sands & Peats – acid ph less than 6
Chalk & Limestone – Alkaline ph above 7.5

Finally it should also be considered whether the site is excessively wet or shady.
With this information, it should be possible to choose an appropriate mixture of wildflower and meadow grass seeds.  If uncertain of the soil type then select a General purpose wildflower mixture.

Site Preparation
It is necessary to create a level firm weed free seedbed. To remove perennial weeds, the site can be treated with a non-residual herbicide several weeks before sowing and re-ploughed or dug over several times to deal with annual weeds. Sand or fine sawdust can be added to the seed to ensure even coverage. Seed can be sown in spring or autumn at a rate of 3-4 grams per sq. metre.