If you are certain that some drops of urine came out, then you have to repeat wudoo’ and wash whatever part of your clothes they got onto. If you are not sure of the place where the drops fell, then you can wash the area where you think it most likely that the drops fell, until you are sure that the najaasah has been removed.
It says in Zaad al-Mustaqni’: If the exact site of the najaasah is not certain, (the person) may wash it until he is certain that it has been removed.
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said in his Sharh: i.e., if any kind of najaasah gets on anything, and the exact site is not known, the area where it is thought to be must be washed until one is certain that it has been removed. It should be noted that one of two scenarios must apply with regard to najaasah: the area touched by it will be either small or large. If it is a large area, he should check thoroughly, and he should wash the area where he thinks the najaasah touched it, because washing the entire area may be difficult. But if it is small he must wash it until he is certain that it has been removed. End quote from al-Sharh al-Mumti’ (1/435).
If you know that these drops come out when you lift up your feet to wash them in wudoo’, then you should not do that, rather you can wash them on the ground by pouring water over them. If you are not sure whether anything has come out of you or not, then you do not have to look and check, rather you have to ignore it, and your wudoo’ is valid and your garment is pure.
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked: When I finish my wudoo’ and go to pray, I feel that a drop of urine comes out of my penis; what should I do?
He replied: What you should do is ignore that and pay no attention to it, as the imams have told us to do. Do not pay any attention to it and do not go and look to see whether anything came out of the penis or not. In sha Allah, if he seeks refuge with Allaah from the accursed shaytaan and ignores it, it will go away. But if he is definitely certain, as certain as seeing the sun, then he must wash the place where the najaasah is and repeat his wudoo’, because some people, when they feel some coolness in the tip of the penis, they think that something has come out. If he is sure then he must do what I have mentioned to you. What you mention is not incontinence, because this stops, whereas incontinence is continuous. But this is something that happens after moving, and one or two drops come out; it is not incontinence, because if a few drops come out and then stop. In this case, he should wash it and do wudoo’ again. He should always do that, and be patient and seek reward. End quote from Liqa’ al-Baab il-Maftooh (15/184).
You could also use a cloth to prevent the najaasah from reaching your clothing, and in that case you do not have to wash the garment, rather it is sufficient to remove the cloth.
And Allaah knows best.