1. I don't feel represented by this Constitution!
That is because 'Constitution' is really a misnomer. The current text is a re-bundling of previous treaties, with a few extra measures tacked on. One can stare oneself blind on the fact that the treaty is no consitution, but that is stupid -- rather, one should weigh the proposed treaty on its own merits.
2. With this new treaty, it will still be possible to have bullfights and force-feed geese!
Those things are also possible now -- the treaty will not change the status quo in that respect. I'm sure there are many things that you want to see forbidden, but should you vote against a treaty because it doesn't forbid those things? I would like to see the act of having loud conversations on your mobile phone in public to be forbidden -- but the treaty doesn't mention that, thus I should vote against the treaty? An absurd reason.
3. There is no mention of social cohesion and social security systems in the treaty!
The EU is, by it's very nature, more concerned with economic growth and regulation than with social security. This is reflected in the text of the treaty. This also means the member states who value such things (Sweden, Denmark, but also the Netherlands) are free to determine their own social security systems!
The bizarre thing is, that the political parties who use this argument (mainly the SP), would never want the EU to have a say in how the Netherlands organises its' social security -- so why complain about this issue?
4. I don't want Turkey to join the EU!
Whether Turkey becomes a member is not an article of the treaty. Rather, the treaty specifies a set of strict rules by which new prospective members have to play. Amongst these are things like "don't torture prisoners" and things like that. This guarantees that only civilised countries get to join the EU.
5. I don't like our current (Dutch) government, and they want me to vote 'yes'!
Your vote against the treaty will not topple the Dutch government. Rather, you should vote against the ruling political parties at the next national elections, when your dissatisfaction really counts for those in power in the Netherlands.
6. The EU is growing too big!
The EU will not magically grow smaller if the treaty does not get ratified. The Netherlands (or any other country, for that matter) will not secede from the EU if the treaty isn't ratified.
7. I don't like the EU as it is!
Maybe that is precisely why you should vote in favour of the treaty. The question you need to ask yourself is not "Do I like the EU as it is now?", but "Will I like the EU with the new treaty better?"
8. The French have already voted against!
So? If 55% of the French jump into a river, will you too?
9. I'm voting against, so that we will get a better treaty!
Who says so? All you can vote is 'yes' or 'no'. There is no option 'No, because...' -- this is not an essay question on an exam! While there is a chance that the next treaty (if/when it will be drafted -- certainly not within a year) will cater (more) to your particular tastes, there is no guarantee that this will be. Perhaps the treaty will be re-phrased in a way you don't want. The question you need to ask yourself is: "Will things get better with this new treaty?", not "Is this (in my opinion) the best possible treaty?" Also, see reason number 2.
10. I just have a bad (gut-)feeling about this!
If you can't support your position with rational arguments, you have no business voting. The last time people voted with their gut-feelings, we got the LPF in the government. I'm pretty sure everyone recognises that as the debacle it was. And I'm pretty sure no-one wants a repeat of that on a European scale.