As practice time is limited, you will want to make the best use of this time in the most efficient manner possible. Below are the steps that I recommend for your practice. There are indications that how you practice things influences the mechanisms and brain regions in/by which the learned material is stored in your brain. Combined with the fact that neurons fatigue within a matter of minutes, this means that a class that is conducive for learning should integrate and intermingle various training methodologies to optimize learning. PLEASE NOTE: If you don't want to read all of this, at least read the "Sparring" paragraph.
First, you must see the technique, and learn the steps and details on how to perform the technique. This can be through in class live instruction, or from watching the instructional videos. It is important in this instruction, for the instructor to not only detail how the technique is done, but also to explain why you are doing what you are doing. Most importantly, the how and the why should be linked by the instructor to the overall strategies and concepts of successful jiu-jitsu. This multiple linking of technique how and why, with the broader strategic goals will speed learning and increase retention of information.
Single Technique Repetition
The next step is to repeat the technique on your unresisting training partner many times. This helps to lock the steps of the technique in your mind, as well as helping you learn the unconscious body skills required by the technique. These unconscious body skills are analogous to learning to ride a bicycle. Although there are certain things about riding a bike that you can teach, like how to start the pedal, and to turn into the direction that you are starting to fall, the majority of the skills required to ride a bike are unconscious skills, that can be learned only through the experience of attempting to ride. There are analogous skills in jiu-jitsu, and every sport. These sorts of skills will be begun to be mastered here, and further expertise will be gained in the drills below
Once you have a basic understanding of the technique, and have practiced it a sufficient number of times to be reasonably proficient, the next step is to link this technique together with other techniques into a "chain" as might be used in sparring. Single technique repetition is good, but as neurons fatigue quickly, by chaining several techniques together, the neurons that are being trained for each technique get a chance to rest while you are completing the chain. Additionally there is evidence that these different practice methodologies modulate different brain structures, so utilizing both single technique repetition (constant practice), along with chain drills (variable practice) will likely speed learning (Link: Neural substrates of motor memory consolidation depend on practice structure).
Chain Flow Sparring (French Randori)
Now the basic learning and motor skills should be in place for the techniques. The next step is to work the techniques and chains against a lightly resisting opponent. The opponent moves and defends as he normally would in sparring, but utilizes a very low level of strength and speed. This allows for success every time, as long as the technique is performed properly. This practice helps to find defects in the way you are performing the technique, and starts to build the conscious and unconscious skills to a high enough level necessary for performance of the technique in actual sparring.
Specific training limits the area in which you are training so that you can focus on practicing, against a fully resisting partner, the techniques or chains that you are currently working on. For example, the techniques instructed in the class might involve passing the guard. Specific training is where you start in your opponent's guard, and try to pass. Meanwhile, your opponent is trying to sweep or submit you. When either of these goals is accomplished, you restart back in the guard. This way, you stay focused on practicing and integrating the techniques you just learned. When doing specific training you should try to limit what you are working on during any session to just a couple of passes, and 2-3 attacks from the guard. This way you can actually develop a good level of skill with a few techniques. Once you have acheived suffiecient mastery of these to successfully use them in sparring, you will be ready to move on to another group of techniques.
Sparring is where both participants are fully resisting. The only caveat is, strength and speed should be limited just a little, so that control and safety are maintained.