They say never mix love and money, but ultimately we all have to. Financial problems are one of the major causes of relationship break-up, so taking a little time to think about how you manage them is always worthwhile.1. Opposites may attract, but they shouldn't have a joint bank account.Many members of the older generation have completely joint finances. And I certainly am not going to tell them they're wrong.Yet times have changed and many couples these days have spent a substantial period of financial independence before they get together. These can mean joint finances can cause rows. So discuss carefully before you do this, is one of you a spender and the other a saver? This can be a nightmare, and it's best to steer clear of joint accounts.However that doesn't mean you need avoid a joint bills account which is often a useful way for those with separate accounts to work. The amount you both put in should be decided between you, it doesn't have to be equal if your income and expenses aren't.People often ask me: "What's the best joint account?" The answer's simple - almost all accounts allow you to hold them jointly, so it's the same as for a single person.2. Bad debt is more like an STI than a marriageYou can be as love-struck as Romeo and Juliet (and we all know how that ended), but what lenders care about is the financial products that link the two of you. There are only two types, a joint bank account or mortgage (joint credit cards don't exist, just second cardholders). If you have one of these, it connects your credit files - meaning if you apply for credit, your partner's finances are likely to be looked at too. Therefore, if one of you has bad credit, it can impact the other.The reason I liken it to an STI is that if your relationship breaks down, separating or getting a divorce doesn't make the linkage go away - problems can linger long after. The solution is to apply for a 'notice of disassociation', but only if your finances are truly separate - if you still have a house or joint finances, this won't be granted.In a nutshell, be very careful before getting any products with someone who has a bad credit history - no matter how much you love them!3. You both need to take an interest"My partner deals with all the finances - I haven't got a clue." If this sounds like you, then alarm bells should be ringing. Let me be blunt, imagine for a second that the worst were to happen and your partner died or left you - this would leave you with untold financial disorganisation grief on top of the misery.While it's common for one half of a couple to be better with money than the other, you both need to be involved. I suggest the 'senior' financial half creates a simple factsheet detailing all your products (avoid noting down sensitive passwords though), and that you arrange a budget and finance meeting across the kitchen table to discuss it at least every three months. That diminishes the risk of problems.Budget meetings are also great for those who struggle, so discuss before you spend any money as two have better discipline than one.4. You CAN use a 2for1 voucher on the first date (and every date, in fact)Worried about whipping out that crinkled up 2for1 restaurant voucher on a first date? Don't be. A poll of over 6,000 users on my website shows that being savvy is officially attractive!The scenario was a man asks a woman out and says he'll pay - but uses a 2for1 voucher.30% said using a voucher was a good thing, it shows he's a keeper.56% say it's not an issue.14% say it's tight and avoid.So don't be ashamed, especially not if you're with your partner this Valentine's Day.If you want to go out for dinner, but are on a budget, don't do it on the day itself, go a little bit before. Prezzo has a 2for1 for £2.50 up until Thurs when you register on its website. Loch Fyne has a 25% off on its site too, and Bella Italia has 30% off as well.On the day itself, there's not too much around - there is a 2for1 Pizza Hut Delivery for a night in, a Harvester £9.99 main, unlimited salad, soft drinks & pudding deal. Or a voucher for 2 GBK Burgers for £10 on its site.Then there's Dine in Deals for two. Morrisons has mains including rump steak, dessert and two sides for £9; Sainsbury's £10 deal gets mains including bistro chicken with red wine, dessert such as chocolate souffle, and a bottle of wine; M&S £20 deal includes starters, mains including beef wellington, sides, desserts such as millionaire's shortbread, box of chocolates and a bottle of wine such as a Rosado Cava.5. Trust pays in a relationship (and in your finances)If you're in a trusting relationship, you can use that to gain financially. If you're married or in a civil partnership, a classic example is to move any savings you have into the name of the lower rate taxpayer to maximise the interest payments. You can do this if you're not married, but then there's a minor risk of inheritance tax issues if one of you died and you have substantial assets.Another tip is to use cashback credit cards to maximise gains and prolong bonuses. My top pick is the Amex Platinum Everyday - which pays new cardholders 5% cashback for the first three months on up to £2,000 spending. The trick is for one of you to sign up to the account and get joint cards so you can both spend on it. Once the three months are up, get your partner to a new card to keep the 5% for another three months. Remember to always REPAY IN FULL each month or it's 19.9% representative APR.Or for bank accounts, as each needs you to be earning to get it, one of you can get a Santander 123 current account - which, while it has a £2 a month fee, pays cashback on bills, eg. 3% on phone, 1% council tax, and 3% savings interest (if you've £3,000 to £20,000). So that person becomes the bill payer, the other can then go and get an account such as First Direct which gives a £100 switching bonus, top rated service and a 0% £250 overdraft.