What I should if I wanna buy a new bass and how to try a bass??

Pick up the bass. Play it to see if you like it. Consider whether to ask the opinion of people on the Internet, then decide "no" and choose to trust your own judgement as to whether you like it.* If you do like it, find the person who is selling it and pay money to them until they let you take it away.



*Unless you have specific questions about a particular bass, such as whether the quality of Fender is bad. A brief search of this forum should help you answer such questions.

 

the tone preference is up to you, play a bunch of them and pic the sound you like, play them through the same amp with the eq set flat, if you make adjustments make the same ones for each bass, try each one flat but also try each one with some tweaking of the controles, different basses have certan adjustments that make them shine that's why amps have eq's.
play each note on the neck to make shure theirs no buzing from the string rattling on a higher fret, a little extra treble in the eq makes this easier to here.
look down the leingth of the neck on the edge and make shure it's straight, a slight amount of bow is ok but a lot could be a sign of trouble.
I personaly feel fender basses are overpriced and have poor quality controle, the higher priced ones are a gamble if youll get a good one and the cheep ones are just terable
for a good quality mid range priced bass I like Ibanez soundgear basses for higher end 1-2-4K$ I like spector

 

It's sounds to me like you are new to playing bass. Your questions are good ones for someone just starting out. Imo with all the information you are asking for here I think your best bet is to either find an experienced bass player where you are who would be willing to show you the ropes so to speak. Do you know anyone like that?

Another option would be to find a music store that's trusted by other players where your questions could be answered by someone there with some experience and knowledge. This would also get you out there putting your hands on a variety of basses so you can start to learn the differences and make your own judgments about what sounds good to you. Best of luck to you.

 

see how much it weighs . . . heavy basses are cool, but if you play a lot with a strap, it could cause pain after some time

 

Until you've played bass you won't know what tone means. Once you've played even for a few weeks, and however badly, you'll find that if you try a bass or two in a shop you'll hear and feel surprising differences. If you can possibly borrow any bass at all just for a short while you'll discover more about what you like than any TB post can tell you.
It's like anything else: riding a bike, driving a car, swimming, your first ever date: you've no idea until you have just a little experience.

 

Take advantage of the 30 day return policy (most stores and definitely Guitar Center) when trying it out.

 

Make sure any instrument you try out is properly set up. The strings should be relatively close to the frets/ fingerboard, and none of the notes up and down the neck should buzz or not sound (this would indicate a high or low fret).

You don't want to set everything to 'zero', bur rather 'flat'. All amps are different, but flat is usually found when all EQ (bass, middle, treble) are set at 12 o'clock (the indicator on the knob should be straight up).

Turn the volume on the bass, not the amp, all the way up, regardless if it has one pickup or two or three. Play things you are comfortable with and then go ahead and adjust the knobs on the bass (volume, tone, EQ, pickup switch, etc.).

If you feel like the instrument has enough range of tones, and plays well (no high or low frets), check it out for imperfections. This is good to do when the salesperson is around, because if you find something minor wrong (paint run, scratches, stuff like that) you can use it as a point to haggle the price lower.

Remember, no matter where you go, most instruments aren't set up well, if at all. The strings may be miles from the fretboard, or the strings themselves could be rusting and horribly out of tune.

Don't let anyone else's opinion sway you from getting something from a brand you desire. Some Fender stuff does have poor quality control... thats true of every brand except maybe custom handmade stuff. I will agree that Fender tends to be a bit overpriced. The stuff made in Mexico is definitely overpriced. Made in USA, or Japan... not so much, but there are always cases of crappy instruments. If you want Fender style but don't want to pay Fender price, look at Squiers in the Vintage Modified and Classic Vibe series, even the Affinity series stuff can be pretty decent for the money.