Understand the weather and you will probably stay in the sport a long time, head out too many times on the wrong day and you'll quickly get disenchanted and give up.
If the wind is forecast to be between 5 - 15KMH, the chances are it will be somewhat flyable, as soon as you go beyond that it gets a little more complicated, but if you use the right websites it really isn't that hard.
Get a consensus
You can now get access to a range of different weather forecast models for free through windy.com (which also has an app), this will allow you to check ECMWF, ICON, GFS, MeteoBlue and AROME. If all the forecasts are saying the same thing, the chances are that the forecast weather will be the weather on the day. If you click on a location, you can then click compare when the 5 day forecast appears and see all the forecasts for the days ahead. For belts and braces, check the metoffice too.
Check How gusty is the wind
Gusts can indicate thermals, but the more gusty the wind, the more your wing will pitch and the more dangerous the conditions are likely to be. If the forecast is for gusting much more than 20KMH, chances are it will be blown out for you, especially in the early days.
Check flying weather sites/apps
These days there are numerous paid for forecasting sites that will give you an indication of how good the day is going to be with a simple colour coding as well as a few free ones too. Once you've got to grips with them, they are a treasure trove of information, but can seem a little daunting at first (they aren't if you give them a few minutes, but here is a quick summary to look for)
Cumulus Cloudbase / maximum climb
the maximum height that you'll get to on any given day. In simple terms, the greater the differential between the night time low temperature and the day high, the higher cloudbase will be. If you know the dew point you can also do (temperature - dew point)/2.5*1000 to give cloudbase in feet. In the UK anything over 4000ft is good, 5000ft is excellent and 6000ft exceptional (but watch out for airspace)
The layman's approach, If it is a 5 star day, it is almost guaranteed to be an amazing day to go paragliding, but it will probably be busy. The star ratings are calculated by working out the thermal strength, the maximum thermalling height, sun on the ground and the wind.
The stronger the thermals, the easier the day will be, but conversely the stronger the sink will be between the lift.
Look for convergence
Most easily done using windy.com, zoom out on an area and you will be able to see the winds coming together and areas of slack air.This is usually convergence and an indication that the air is going up rather than along, this can be great if you are looking fly along the sea breeze front, but the convergence will move through the day, so watching out from it even if far from the coast is sensible.
Ask other pilots
Don't just ask any time you're thinking about flying as people won't be very helpful. However, if you post that you are thinking about flying on a particular day because of a bunch of reasons, you'll usually find a great deal of help comes your way.
Check the satpix on the day and nearby webcams
The forecasts aren't always quite right and occasionally the band of cloud isn't quite where it was meant to be, checking the satpix before heading out can be a very good way to avoid a wasted journey.
Understanding Skew Ts