What I should carry in my suitcase?

When I leave for trips that last at least a week, the "bigger problem" is  just what to bring. I usually ask myself things like "What do I bring? "? "Then if the weather is cold?" "And if the weather is hot?". Well I'm always afraid of not having enough or having too many things, even though the end is almost always the latter case true and I always pack a lot of things that remain unused (and thus take up space that could instead be used for things like gifts for friends and family or for myself).

The first things that I would consider are:
1) In what season we are;
2) where I'm going (from Italy to London, surely the time will change for the worse);
3) baggage that I want / need to bring;

Now we begin to analyze these three points from the first: the season when we leave. If the city where we go is colder than the city where we live, we need to bring warmer clothes. I know that this reasoning is obvious to all of us,but it is an argument that we usually do only after putting the clothes in the suitcase and we see that we can't put all in the luggage.
We continue with the consideration of what will be our goal. For example, if you depart from Rome and go to London you know that there will definitely be cooler than in Rome and you know you should wear something that shelters from the cold.
What about the luggage to use? I usually have several options from which I can decide, even by mode of transport bywhich arrive at its destination: car, plane, bus, train, etc.. I always prefer the trolleys to travel, both in Italy and abroad, using any means of transport, the bags are best because very comfortable to carry. Of course, strictly soft trolley, as if I wanted to bring one more thing there is less risk that I bangs the bag. At this point we have to distinguish: if I'm in the car, I don't worry too much about the weight of the luggage I carry with me and maybe I carry a bag more with what I want to take with me but was not included in the main case. If, however, left by plane, then I do make a distinction between hand luggage and hold baggage and I have to pay close attention to the weight of luggage and each company sets a different weight.
Now we have "only" to put things in the suitcase: the first thing I pull out everything I want to take me and put it on the bed (or on your desktop) and I put everything sorted shirts, pants, sweaters, etc.. Now, since I certainly do not all come in bags, I start to do an initial screening by setting aside one to which I would not give up.At this point I put in the closet things that I don't carry with me and instead I put in the suitcase what I bring for the travel. It happens many times but fail to deliver good things and I have to start over at least a couple of times! I start from his trousers .. Above, then, put your shirts and sweaters. For shoes I leave a side room.The laundry of course above all in bags that hold it separate from the rest, or in the pockets of the suitcase.And the things for bathroom? If I use a carry-on baggage of those kits that are in different perfume bottles and have to be filled with shampoo conditioner and shower gel. To take the toothpaste tubes small (or buy it directly to your destination). For the face I carry the wipes that can be useful when I'm around and I want to freshen up a bit (there are all the brands) and cleansing wipes to remove makeup, or if I find some small pots, I carry a makeup remover . The hair dryer, put it in my suitcase if I'm not in a hotel or if the hotel does not have a hairdryer in the rooms (but I always found. Usually there is always one).
And for the things that I can carry in hand luggage (such things as hand nail scissors)?If I leave for a week, I take a couple of hours the day before departure when I can devote myself to the beauty and my body. Then placed the nails of hands and feet (cutting, silt, get your nails). I make a face mask, do the body scrub. If I go for several days I carry a nail file (not those of the nail kit that obviously can not bring), I do not get your nails done before you leave, but I carry a single enamel so that if I want to put, I put it when I'm out (everything else I do it anyway before you leave).