Don't feel uncomfortable about having to stick to a budget or worry about pairings.

Ordering wines in a restaurant is something that should be looked forward to, rather than dreaded. The aim is to find something that you can both afford and enjoy. So, you are looking for something that will go well with what you are eating and is in the correct price range. Here is my approach. It is really about narrowing the choices and then making a selection from a few wines, rather than many.

Firstly, work out what price you are comfortable paying - we all have our own number, whether we are a billionaire or on a modest salary. Secondly, listen to what everyone is going to choose to eat and ask what wine they would like: white, red, rose or champagne - you don't have to worry about sticking with a historical pairing (e. g. must have white with fish), as it is you who is drinking it not anyone else, but do bear in mind what might go best for everyone. Thirdly, having made your decision on what you need (white only, red only, red and white etc) and price, you look at the wine list and see what options fall into those categories and what looks like good value. You are narrowing the selection and then can order what you looks good value and appeals to you.

If the wine list does not have an interesting list of wines/producers, it is generally best to go for a very safe option - perhaps, a standard but rather boring producer from a good vintage, but at least you know it will be enjoyable. A dull wine list, generally means that no one in the restaurant knows or cares about wine, so safety first is best! If the wine list has lots of great producers - clearly there is someone there who knows what they are doing - you can be much more adventurous. This also applies to how they are likely to have stored the wines - some restaurants may have kept their wines, particularly whites, too long and so I generally will always choose younger, fresher wines - better too young than too old.

With regard to asking for help from the sommelier/waiter/manager, again I would apply the same principles : if the list is interesting, then they should know about it and can make a good recommendation. If the list is dull, their recommendation is more likely to be the wine on which they make the highest margin!

If you this is a business dinner, my best tip is to be well prepared, as there is nothing worse than fighting with the wine list, while you want to talk to your client - see if the wine list is on their website or call ahead and ask them to email it by pdf. Then you can do your research, make some advance selections and narrow your choice down to a few options. Then, all you have to do at the restaurant, is ask what everyone would like to drink: white or red?
Also, when selecting which wine to drink, remember that the following are very important factors which will affect what you choose.
I call this is the MFD: mood, food and dude:

MOOD:
Are you happy? Jubilant? Tired? Irritated?

FOOD:
what are you eating?

DUDE:
who are you having lunch or dinner with? This also affects the budget.

CLIMATE:
is it hot or cold?
Finally, there is one delicate matter to address: do you tip on the just the food or on the food and wine combined? I generally favour the latter, but when I am paying the bill, I'm rarely buying the most expensive bottles.
Here is where I think you want to end up: eating in a restaurant is meant to be a joyful and happy experience, where you leave feeling content. The last thing you want is a bitter taste on either your part or the staff in the restaurant - hopefully, you want to go back! So, if you are not happy tipping on the whole bill (which will always make the staff happy), you need to be generous enough that you have the respect and enthusiasm of the staff for your next visit. If you are not sure, choose generosity over being cheap - you will sleep better that night.