'The Barbell Hip Thrust' is a great glute training exercise. It's very easy to perform, it's usually very safe and you are very unlikely to hurt yourself. The exercise is very versatile as you can use a host of different equipment too. Making it so you can perform this movement at any gym and vary it accordingly (for instance, during pregnancy a barbell can be substituted).
Many women struggle attempting to increase muscle size of the glutes without increasing the size of their quads. Squats may be able to build you a better booty, but squats do not isolate the glutes and other muscles will also grow simultaneously. Whereas, cable kick back exercises may isolate the glutes, but don't allow for enough load to optimally stimulate the muscle fibres promoting growth. Hip thrusts are the answer!
For ideal performance of the hip thrust you rest your shoulders on a box that is approximately the same height as your tibial tuberosity or in English the box should be just underneath your knee cap. The Tibial Tuberosity is circled in red below.
We want your shoulders to be this height because when you thrust up to the top position of the movement it should mean that your ankle and knee are at 90 degrees and the hip joint is extended 0-20 degrees (your torso is in a straight line parallel with the floor until you reach the knee) which is the position where the glutes are activated to the highest degree (assuming good technique is being performed).
When setting up for this exercise if you struggle to get underneath the bar or suspect that you might then you might want to place the plates of the loaded barbell onto an elevated surface like lifting blocks or just rest them on a couple of other weight plates so it's easier to fit underneath. A smith machine can be a great option for this too.
The bar needs to be placed across the hips, just between your hip bones and pubic bone. Make sure you have a cushion for the bar because you don't want a bar pressing directly onto these areas! If you need a wee don't think you can just go after your set by the way. Play it safe and wee beforehand! You'll thank me for this later I promise!
Many people struggle with where to hold the bar. Hold the bar as you would for a normal barbell bench press with the thumb around the bar slightly wider than shoulder width. Grasp it firmly so it won't escape anywhere. Make sure you are in the middle of the bar with your hips touching the cushion, your shoulders are resting on the box and your torso is about 45 degrees in relation to the floor (as pictured below). From this position thrust up powerfully. Keep your head up and look towards the bar and this will help increase glute activation further. More glute activation should mean more glute muscle which is always a good thing! At the top position you can pause for a second or two then return to the start position slower than the speed you thrusted upwards. This will train the glutes harder than just dropping the bar to the floor because controlling a muscle as it goes 'down' is another effective way to build more muscle.
You'll see many people performing this with very light weights and not going heavy. I like to use both. Most people can start at about 50kg in total and work up from there. Try to use a rep range of between 5 and 15 repetitions for between 3 and 5 sets at first then once you've nailed the movement you can go on to play with all kinds of rep ranges.
If you've been hip thrusting for a long time and need to mix it up perhaps try a single-leg variation. It's tough as hell. Start on your weaker side and see how you find it.